I don't either, Jeri. So I checked Wikipedia and here ya go. It's actually understandable:

"Clawhammer vs. frailing
While the terms "clawhammer" and "frailing" can be used interchangeably, some old-time players draw a distinction between the two. On the banjo, frailing most commonly means always picking the drone string, while clawhammer allows the picking of other strings with the thumb, which is also called "drop thumbing". Some players further distinguish between "drop thumb" and "clawhammer", in which the thumb plays rhythm in drop thumb, but melody in clawhammer. There is also a known style where two fingers are used brushing down described as "Knock-Down". There are yet more variations of the distinction between "clawhammer" and "frailing", but they all refer to the same general style of playing. The term "double thumbing" is sometimes used interchangeably with "drop thumbing", though double thumbing refers specifically to striking the fifth string after every beat rather than every other beat, while drop thumbing refers to dropping the thumb from the 5th drone string down to strike a melody note."