Understand it implies shifting a problem, not fixing it. Borrowing money just rob Peter to pay Paul; it doesn't erase the debt.
Pro Tip 2/3
Zero-Sum
It's often used in situations where resources are limited, and solution doesn't increase them. Cutting healthcare to fund education is just robbing Peter to pay Paul.
Pro Tip 3/3
Negative Outcome
Using the phrase generally suggests a negative view of the situation. The government's plan is robbing Peter to pay Paul, ending up helping no one.