Cash Contests are contests in which you participate by paying an entry fee and compete with others to win Cash Prize.
The prize money will be given to the winners who have the highest points in a specific contest. Different Contests have different winning amounts and will also have a different number of members.
If you need to gain your skills, join a Practice Contest for free and the beauty is you'll get Cash Prize if your team comes first. Once you're confident of your skills, you can join Cash Contests.