Events are created by the Wwise user, specifying actions to be performed on Wwise objects. For example, an event might contain a Play action on sound Bird1, and a Stop action on sound Bird2. A second event could contain a Set Volume action on sound CarEngine, setting a relative volume offset of -2, and a Set State action that changes switch group Ground_Material to Tiles.
Events are then packaged into SoundBanks which can be loaded in your game, after which those events can be triggerred by your game's code. For example, when the player enters the kitchen, you would trigger the event that sets the Ground_Material state to Tiles.
Once events are integrated in the game, the Wwise user can continue working on them, changing or modifying the actions they contain, or the objects to which they refer. Since your game is still triggering the same event, the changes made by the Wwise user will take effect in the game without requiring extra work from the developer, and without recompiling the code.
Refer to the Wwise documentation for more information about Events from the point of view of the Wwise user.
Refer to Integration Details - Events for an overview of the integration of events in your game.