A "reverse" is part of standard bidding. All bridge players use it, whether they realize it or not. Understanding reversals is good for your bridge, your health and your safety.
So What is a Reverse?
Opener: Provided your partner has responded at the 1-level, the requirement to bid a new suit at the 2-level that ranks higher than your first suit, is 17+ points.
Reversing implies greater length in your first suit (usually 5-4, but maybe 6-4 or 6-5.) Reverses are forcing for one round.