Rat means to make one (or a few) suggestion(s) how to solve a problem or how to decide between several options. Beispiel: Ich habe Problem 123, kannst du mir hierzu einen Rat geben? - Wenn ich du wäre, dann würde ich XYZ machen. Ein Rat ist ein Lösungsvorschlag, eine Entscheidungshilfe. Beratung is the process of finding a solution for a problem. You describe your problem (sometimes you might need help with this, too) and then discuss it with your consultant. In the course of your discussion you work out a solution together. Of course your consultant may as well present a solution but beyond that they will inform you about all of its advantages and disadvantages, so you can make your own decision. (Is it necessary to mention that in practice this is not always the case?)

What does your dictionary say?