Hey John,
As the wiki says that's a really big club.
In general you don't want to use it, unless you want to slow macros down more than necessary. A judicious use of pause is usually more efficient.
Keyboard Maestro's documentation is not written in such a way that it's easy to read from beginning to end.
A good place to start is to become familiar with all the actions, tokens, and functions:
List Keyboard Maestro’s Actions, Functions, and Tokens macro
-Chris