Events can be set to do many things, such as spawn projectiles. In game, they are shown simular to this.
[OnActivate] [Player] [AddHealth ] 
The "[OnActivate]" is the input event, the event required to happen to trigger the action. The "[Player] is the chosen target, meaning it will effect the player character who triggers it. The "[AddHealth]" is the effect. It will ail 25 health points, restoring back to a greater value of healthiness. The "" is the variable, being the magnitute of the effect. Occasionally such events will be on a scale bar, depicted like "<--|--|--()--|--|-->", with the "()" being the slider at default value. Such events using this are events such as "SetPlayerScale". A more complicated way to do this would be;
[OnActivate] [Player] [AddHealth]  [OnActivate] [Self] [Dissapear]  [OnActivate] [Self] [PlaySound] [wandHit] [OnActivate] [Client] [ChatMessage] [25 health points restored]
This would make it so the brick would fade away after the player clicks it, play a sound effect, and heal the player. The brick will respawn in a bit. This would prevent it from being clicked rapidly to almost instantly restoring all of the players health, and add a bit more of an auditory effect to give the "feeling" of being ailed. It would also tell the player that they were healed.
Numerous players have created their own complicated mini-games through the "events" system, as illustrated in this video. Some servers are entirely dedicated to eventing.