Preparation is the act of preparing — getting ready, planning, training, or studying with a goal in mind.
If you know pre means before, then you have a clue to the meaning of preparation. Dressing up before a date, learning your lines for a play, and attending medical school are all forms of preparation. Boot camp is preparation for soldiers. Rehearsal is preparation for actors. In cooking a huge meal, you have to do a lot of preparation before actually beginning to cook. If you fail a test, you clearly need to do more preparation next time.