You will find several items in the server that can be equipped.  
Skins, Hats, chest pieces, pants, shoes, and rings can provide bonus defense to your characters total armor value.  
Backpacks can increase the amount of weight you may carry around.  
Your primary, secondary, & melee slots let you kill things... Duh.  
Your tertiary slot can be used for grenades, a medkit, a portable shield kit, a pickaxe, or a fishing rod.  
The ring slot is used for providing your character with bonuses that are not found on other equipment slots. These can be used to alter movement speed and armor.  
You can also obtain pets. These little fellas provide you with slight buffs and bonuses, so don't forget to equip one and feed it.

Related Topics: 5.1 Boss Sets, 5.2 Repairing