Precise methods and definitions vary with country, bidding system and partnership agreements.
Thus the reverse has forced the partnership to commit to taking nine tricks instead of eight - based on the extra strength of opener.
Since a two-over-one response shows more than a minimum, generally ten or more, opener does not need as strong a hand to reverse the bidding at that juncture.
The modern trend is therefore to allow such a reverse bid after a two-over-one initial response with a minimum opening hand.
Reverse bids are generally considered to be forcing, with subtle variations depending on system: These examples illustrate high and low level reverses: In some variants of 2/1 game forcing, the major-suit reverse after the sequence 1♦ – 2♣ doesn't promise extra values — opener may merely show a 4-card suit or a stopper.
Jump reverses after a minor-suit response commonly show splinter raises, too.
This agreement facilitates partner in deciding the final contract (in most cases 3NT or a game or slam in the opened minor).