“Racket” is both a noun and a verb. You may know that it is used in tennis (raqueta). That is easy.
“Racket” has other uses. A racket can be a loud noise or a lot of noise (estruendo) from machines or people (follón). A person can “make a racket” (hacer ruido) or make a lot of noise, and it is unwelcome.
Some people are involved “in a racket”, which is usually illegal. A racket could be an organized fraud (una estafa). In the newspapers we often read about the “drug racket” (el tráfico de drogas).
A connected word is “racketeering, a noun which refers to organized crime (crimen organizado).