Pre-Hardmode items

Pre-hardmode is the de facto name for the state all worlds generate in, otherwise simply referred to as New World. While the title "Hardmode" implies that the early game is simple or not difficult, it is still a fairly dangerous and complex place in its own right.

The First Nights
One of the major challenges of pre-hardmode is the fact that it is often entered into by new characters, and in fact even new players unaware that there is a "hardmode" later on. Even those experienced with the game can encounter difficulty with simple tasks like remembering how many iron bars are needed to make an anvil, or how deep and far one has to venture for overlooked necessities like hooks.

Because of the way Terraria's progression works, using a system heavily based on gear progression, players grow more and more powerful as time goes on, meaning that the period of most difficulty is when no progression at all has been made. The miserable state of a newly created character's barely functional stab-sword and tools often saddled with negative modifiers means that while players in hardmode contend with the awakening of evil spirits and the spreading of primeval forces that consume and destroy all in their path, a player in easymode faces deadly peril from something as mundane as a thirty-foot fall or an ill-timed trip too far into another environment.

Prior to Hardmode, armor options are much more limited, and the ridiculous set bonuses earned from the variable-helmet hardmode armor sets are almost entirely absent. Most wood and subterranean metal armors offer only moderate increases in defense as bonuses for wearing the set, while still requiring hundreds of ores to craft (or in the case of wood armors, being useless and looking ridiculous). Even so, this defense is necessary, and worse, the choice must then be made between using those bars to upgrade one's tools or improve one's survivability.

Unseen Challenges
Even for a well-equipped character, easymode can still prove to be a thorn in one's side. Money is much harder to come by prior to hardmode, where enemies routinely drop silver and gold coins in the dozens- by comparison, the Jungle Slime's 5 silver pieces is considered a fortunate bounty. For characters heavily reliant on bullets and potions bought from merchants, money is often in shorter supply than usual.

Almost needless to say is the fact that a player won't have access to hardmode ores, so someone using hardmode equipment in pre-hardmode is effectively locked in their progression. This is primarily an issue when using Chlorophyte Bars to craft ammunition- the ore won't spread at all in pre-hardmode. Likewise, most of the higher-tier merchants are entirely unavailable during pre-hardmode, and those that are often have dramatically limited selections. Forget about crafting tens of thousands of Golden or Party Bullets to alleviate your money woes- you'll have to make do with Musket Balls until the next Blood Moon. Hope you brought a lot of Rockets!

So?
So, the point of this guide is that pre-hardmode isn't necessarily easier or harder, just different in its difficulty. You'll likely have noted that most of the problems one encounters in pre-hardmode are related to managing and acquiring resources. Enemies exist, but their AI is simplistic and they're not too strong- with the right tools, even a blood moon can become trivial. The trip to hardmode is entirely a game of testing one's ability to use resources effectively. Grappling hooks are considered such a necessity that there's a quick-grapple built right into the keybinds, but to make your first- be it the first Grappling Hook or one of the gem variants- you typically have to go underground, braving the dark chasms and deadly falls that you'll eventually use it to navigate. Likewise, the Nightmare and Deathbringer picks, the first tools that can mine ebonstone or crimstone blocks, are both built using drops from bosses you'll likely need to break quite a few of these "unbreakable" materials to challenge.

Essentially, progression in the early game is achieved by surviving in an adverse environment until you acquire the tools and resources to tame it, then using those tools to move onto the next. The ultimate goal, of course, is to arrive at the Underworld and defeat the Wall of Flesh, a boss that requires a combination of careful preparation of terrain, proper equipment and good mobility.

Surviving Easymode
Of course, getting by entirely in a pre-hardmode world isn't impossible, and there's nothing in hardmode that one particularly needs if they're not in hardmode. In many ways, hardmode is a means to extend playtime once the player has achieved a post-scarcity state- while you'll have all of these material issues early on or transferring between, for a "midgame" character it's a pretty sweet deal- you'll have conquered the dungeon and picked up several interesting and powerful levels, and the last boss remaining neither invades at night nor bars your progress through an area. One can, in fact, see everything the pre-hard Underworld has to offer without ever encountering the Wall of Flesh or even the means to summon it. Few enemies pose a challenge at that point, and those that do are often far off. The only real danger comes during the Blood Moon, and even then it's mostly a risk to your NPCs moreso than yourself.

Staying in Easymode

 * Many players are dead on arrival. Something that happens far too often is that a player kills the Wall of Flesh, only to slip and fall into some lava, dying- and for non-softcore characters, losing the gear they needed to kill the Wall in the first place. You need the Pwnhammer it drops, as it's the only tool a player can reasonably acquire that can smash the Altars that spawn the Hardmode ores. Even if you respawn in the Underworld, you may well find that the world outside your house is too hostile to get to this essential tool- and some who do make it back only find an empty Demonite box.
 * Hardmode can seem somewhat unfair to many players, particularly those that enter unprepared. The popular combination of Meteor Armor and Space Gun make short work of most pre-hardmode enemies, but the Space Gun is functionally useless once the Wall of Flesh is dead- most Hardmode enemies take single-digit damage from it and have hundreds of hit points. Whether or not the Wall of Flesh drops a Hardmode-worthy weapon is entirely a matter of luck, and for a while the Pwnhammer may be the strongest weapon you have. Even if your armor is no issue and you can dodge attacks just fine, a mostly-dead mechanical boss flying away at sunrise is far too common a sight. Using pre-hardmode weapons to fight them may well be numerically impossible.
 * Put simply, most hardmode content isn't immediately available. Even putting aside the fact that you have to go get the materials for most of the new items in a much more dangerous world, most of the content is hidden behind additional barriers, particularly things in the much less well-advertised post-Plantera phase of the game. It might be a long time before you can use that rocket launcher.
 * There are many more involuntary events in Hardmode. Many players enter Hardmode at a point where they still encounter some difficulty with Goblin Armies, making something as simple as a Blood Moon infinitely more complicated when those monsters ransacking your town are Werewolves.
 * If you're big on player versus player combat, it's worth noting that a fair number of hardmode weapons, particularly magical ones, rely on homing capabilities. Going ahead to Hardmode to get more powerful weapons to fight your friends with may backfire when they turn out to be little more than costly Gem Staves.

Moving On

 * As mentioned above, much of the Hardmode content is behind additional barriers. This essentially means that pre-hardmode is more the first third of the game than the first half. A significant amount of content requires you to take that first step!
 * Hardmode has Wings, which are by far the most convenient item in the game. Even the lowest-tier Wing you can acquire easily outdoes almost every mobility-related item available in pre-hardmode. This is just the apex of a massive increase in attack options for players- with new weapons and accessories, magic-themed characters can now do more than just fire differently colored bolts before switching to their gun.
 * Lots of players do like to fight enemies, particularly bosses, and once a player is at the point where they're considering the transition to hardmode it's unlikely the Eye of Cthulhu is much of a challenge. Though Hardmode can be grueling at first even to the prepared, that challenge can in fact be the reason to go ahead with it.
 * Many NPCs are completely unavailable in the early game.
 * There are a few effectively hardmode-only biomes, namely the Hallow and its Underground counterpart, along with subterranean variants of both Corruption and Crimson. The resources and enemies that generate there can't be gotten prior to entering hardmode.