In GWT-platform, what is the different between Action and Event?
I think the concepts of event is a bit wider than action.
Each action can be associated with some event but an action isn't necessarily for a occurrence of defined event.
An action is any action of the user. And an event is a result of user action (UI event) or performing of some conditions (other event).
For example, a user did the action press button. This action can be associated with an event button was pressed. And for example, a event expiration of user session doesn't require any action.
But these terms are very similar in meaning for GWT and I suppose sometimes many developers use they interchangeably.