Casting is the action of activating a spell (or any kind of skill - see note).
Most skills don't activate instantly but require a certain casting time. During that time there is a chance that the casting may be interrupted.
- Note: The use of the term "cast" in Guild Wars is somewhat inconsistent. In some cases it is used for spells only (for example for the Mesmers' Fast Casting), in other cases it applies to all kinds of skills (for example while under influence of the Curse of the Bloodstone).
While casting a character goes through a casting animation which covers the duration of the skill being activated. In addition, the character will strike a pose for a fraction of a second in a cooldown animation before performing the next action.