Terraria has no formal player class or leveling system. However, weapons can be grouped into four ( five) distinct categories based on their damage type – melee, ranged, magic, and summoning. Each class has its strengths and weaknesses and has a wide variety of weapons to choose from.
The melee class is powerful, sporting high defence and damage as well as decent crowd control. It utilizes weapons such as swords, spears, and yoyos. Many melee weapons have a short attack range, and those that are viable at a distance tend to do lower damage than their close-range counterparts.
Rangers are able to attack from a distance, doing high single-target, piercing, or splash damage. They utilize weapons like bows and guns, as well as thrown objects. Ranged users must constantly acquire ammunition, unless using the Endless Quiver or Endless Musket Pouch. This can be done through crafting or purchasing from the Arms Dealer.
Magicians are fragile but highly varied in attack style, often utilizing special mechanics such as homing, lifesteal, and area-of-effect damage. They are held back by reliance on mana, which regenerates very slowly unless the Mana Regeneration buff is in effect. Magic-users must craft or purchase mana potions if they wish to recover mana instantly.
Summoners are good at farming enemies, but most summoning armors have low defense, and summons are often inaccurate against enemies that move quickly. Whips are primary weapons that will focus summons and increase their damage. While many players do challenges where only summon damage is allowed (Whips, Summon weapons and Mounts), the Summoning class was balanced around the idea of the player also using the strongest normal weapon available to them in addition to minions and whips. 
Each class gains more complex abilities as the game progresses, enabling more strategic variety in combat. It is advised for players to try out every weapon they find to help determine what works best for them. It is also recommended to use buff potions and healing potions to increase efficiency and survivability in combat (especially during events and boss fights).
In general, it is recommended to focus on one class. Many armors, accessories, and buffs only benefit a specific class, especially later into the game. Nonetheless, even when not specifically using a hybrid set, backup weapons from another class can be helpful should the situation require a different weapon. Furthermore, each class has at least one minion slot, so it is recommended to have it utilized at all times.
Prior to encountering a boss, set bonuses from wooden and ore armor will almost exclusively provide additional defense, and accessories will not discriminate by weapon type when giving bonuses. When combined with the general scarcity of weapons and the need to survive, there is little point to sticking to a "class" this early on. For these reasons, players are recommended to make use of whatever they can get their hands on. Players can acquire a gun or magic weapon early on by smashing one of the corruption or crimson orbs.
While certain weapons, such as the Blade of Grass, are technically available to the player before fighting a boss, they are difficult to acquire without other post-boss equipment.
With a bit of luck, Fossil Armor can be obtained early on and without much difficulty.
Mages must increase their mana capacity through the use of Mana Crystals before magic weapons become viable. The Magic Hat and Wizard Hat will provide a set bonus when used in conjunction with any robe. Jungle armor and Ancient Cobalt armor can be used interchangeably, with each piece providing the same benefits, and the set bonus being given even when a mix of the 2 armors is used. Depending on the player's skill level, the Demon Scythe can technically be obtained at any point in the game, as Demons will always naturally spawn in the Underworld.
Once you start defeating the first bosses new options become available. In addition, you should have enough mana to use magic weapons. However, the armors still only give small bonuses, so you can still safely mix class styles without a significant loss of damage.
Dedicated summoners are still rather weak at this point, although their summoning items can be used by any class.
Bee armor is preferable if you are planning to use your minions more often and would like to play a more passive role focusing on dodging more than attacking yourself, but Obsidian armor trades 1 of your minions for +20% additional summon damage, and +50% whip range and +35% speed, which can allow for you to play a more aggressive playstyle compared to the traditional summoner.
At this point in time, it becomes almost mandatory to pick a specific class. Many accessories will only benefit a certain class, and armor sets start to benefit only certain types of damage. However, summoner hybridization remains not only viable, but extremely potent due to the availability of the powerful Sanguine Staff.
At this point, you may also want to start working on getting good modifiers for your equipment.
This is the point where a mixed class becomes rather weak compared to a single class, mainly due to there being separate armor sets for each class. You can of course still play a mixed class, though it is recommended to have a backup armor set (e.g. in the vanity slots) so you can switch quickly for some additional damage or defense. Hallowed armor may be preferred for extra survivability. At this point buffs are extremely useful for bosses and almost necessary in master mode.
- For an in-depth guide on how to obtain the Terra Blade, see Guide:Crafting a Terra Blade.
- Due to their high stats, they can be mixed with other armors.
- Due to its lower stats, it should only be used to stack the bonuses of the glove above.
Summoner gains a significant boost to survivability thanks to Hallowed armor. However, it has low offensive bonuses, causing it to favor the Blade Staff (which benefits very little from percentage-based bonuses anyways).
The Tavernkeep's armors provide minion and sentry bonuses while also providing significant melee, ranged, and magic bonuses. Hybridization is required to bring out their full potential. When using the Blade Staff, be sure to use Durendal, Snapthorn, Spinal Tap and Flask of Ichor for best efficiency.
With the Hardmode Dungeon and the Pumpkin Moon and Frost Moon now available, players have access to a variety of new equipment. Furthermore, any Biome Keys you have obtained are now usable. You could attempt to skip this stage by killing the Empress of Light, but most players won't be able to defeat her until they've progressed a bit further.
Both sets of Beetle are viable for different situations. However, the offensive variant is not optimal when using weapons that have their DPS unaffected by melee speed, such as Vampire Knives.
Both the Spectre Mask and Spectre Hood are useful for offense and defense, respectively. The listed hybrid set is strong both offensively and defensively, but is harder to obtain.
The head and leg slots of Valhalla Knight armor can be swapped for pieces that provide minion capacity, while still retaining the breastplate's high health regeneration.
At this point you can start using mixed class setups again, since you can kill everything easily. (except when fighting the Moon Lord).
These setups sacrifice part of their own damage to make boss fights smoother for the entire team. A tank keeping bosses in one place should, depending on your group size, result in the overall party's DPS being higher, due to less deaths, ease of aiming, and no situations where one player runs away with the boss while everyone else chases them. The healer helps increase survivability for their team, but sacrifices large amount of their own damage and defense.