The Assert action (v8+) asserts that the criteria for the conditions are met and aborts the macro if not. If there are no conditions, then the assertion will always fire (v10.0+).
See the Conditions section for further details.
After selecting a condition category you can make further choices. For example, if you choose the Application Condition you can choose a specific application to be running, or at the front, and so on.
Add further conditions by clicking the green + button again.