pause: (time)[, (time)...];
time = This is a regular CSS-style time, eg. 1s (1 second), or 500ms (500 milliseconds or half a second).
This allows a pause in time before running the next action command.
Pauses are specific to the event declaration and the context of the target selector. So the rest of the UI events will continue to operate independently.
The pause command, when used in multiple target selector sets of elements, gives you parallel event flow execution. In other words, you can achieve simultaneous action on multiple target elements by using pause.
For more information about how pauses work internally, or to find out how to make an ajax command synchronous so that your action commands can run in sequence, see the Synchronous actions ("await") page of the docs.
Also, if you haven't already read the event flow documentation, you should check that out.