What is the difference between the As$-$Is process model and the To$-$Be process model?

The process models are not related.

The As$-$Is process model begins with where to implement the solution, and the To$-$Be process model displays why the problem needs to be fixed.

Both processt nodels determine when to solve the problem.

The As$-$Is process model begins with what the process problem is$,$ and the To$-$Be process model displays how the problem will be solved.