In the terminology of Dreamweaver behaviors, an action is what happens when an event occurs.

Thus, Open Browser Window is an action, Swap Image is an action, etc.

(In practice, people tend to say “behavior” rather than “action”.)

Dreamweaver behaviors have changed somewhat from version to version; you may encounter compatibility issues, if you work spans two or more versions of Dreamweaver.

Additional behaviors are available from third-party sources.

You can write your own custom behaviors using JavaScript.

Dreamweaver CS5 and CS5.5 have these built-in actions: