Albion Online's combat is heavily centered around the use of active abilities and passive effects called spells. Your character can have up to six different active spells, all of which come from the equipment you are wearing. As you progress your combat skills on the Destiny Board more spells become available to choose from.
Weapons provide three active spells on the Q, W, and E default hotkeys. Armor pieces each provide one active spell on the R, D, and F hotkeys. Each equipment piece also grants one passive spell (with the exception of plate chest pieces, which grant two passives).
Generally, several Spells will be available for a particular slot, but only one Spell can be active per slot at a time. This choice appears when equipping the item for the first time, but players can change the Spells of their armor any time they are not in combat by clicking on their equipment in the inventory pane.
Note: Damage and healing values shown when hovering over a spell do not take into account all modifiers, such as the damage/heal percentage bonus from chest armors. For this reason your actual values will usually be higher than those shown in tooltips.