It can also include situations where the worker isn’t paid what was agreed.

For example, if you were going to have a 10% commission but the employer lowers this to 2% or nothing, or where a $30/hour rate magically becomes $15/hour after hiring.

They might legally be able to cut your pay by giving notice - this will depend on the jurisdiction. In other regimes, they essentially have to go through the full legal process to fire you.