College prep is an amorphous description of classes suggested for those intending to go to college. Honors Classes tend to have specific higher demand educational/study requirements and are usually recognized as being worthy of special consideration in determining value of grades and/or preparation for college-level work
Some school give weighting to grades for regular classes ("college prep" or not) and for Honors classes, such that - for example - a "B" in an Honors Class might be given the same weight as an "A" ...