What is the difference between having a cleft lip and a cleft palate?

Location, location. A cleft palate is just that, a clefting isolated to the palate. A cleft lip is isolated to the lip. People can have one or the other or both.
Gap in lip or mouth. A cleft lip is a gap in the upper lip on one or both sides. A cleft palate is a hole in the roof of the mouth, either in the back near the uvula, or going forward all the way to the gum line. You can have either cleft lip or palate, or both.