Category puzzles are open solution puzzles. A category is listed, and your job is to give answers that fit that category. For people only last names are valid, unless the person commonly goes by another name (e.g. Madonna). No duplicates are allowed; thus you could list "Madonna" for M, or "Madonna Ciccone" for C, but not both.
In a Category Swarm, you give as many answers as possible. Your score is equal to the number of valid answers you give.
In an Alpha Category, you give up to one answer per letter of the alphabet. Answers with more than one word are allowed, and you get one point per word starting with that letter. Therefore, scores over 26 are possible.