A blackout is when a user connects to a stream but gets an on-demand file or a different station's stream instead of the live stream. It’s used for blacking out certain audiences due to licensing issues.
For Example: If a station only has the rights to stream a baseball game for the local audience, the out of market audience is blacked out and gets the on-demand file.
A whiteout is when no ad insertion is done for a period of time. It’s used when you want to simulcast the live stream. This also typically has to do with live sporting events.