Recently I earned 5 of them, but don't know what they are any idea?
Cycles are also known as upvotes. You can see the number of cycles you have after your username in PARENTHESES. They don't serve any real purpose, but if you have a lot then it means you have been helpful to people on repl and/or have shared a cool project that people have upvoted.
You get 5 cycles if someone marks your answer as correct.