When an event declaration includes a static modifier, the event is said to be a static event. When no static modifier is present, the event is said to be an instance event.
A static event is not associated with a specific instance, and it is a compile-time error to refer to this in the accessors of a static event.
An instance event is associated with a given instance of a class, and this instance can be accessed as this (14.5.7) in the accessors of that event.
When an event is referenced in a member-access (14.5.4) of the form E.M, if M is a static event, E must denote a type, and if M is an instance event, E must denote an instance.
The differences between static and instance members are discussed further in 17.2.5.