Transfer Mechanism
Responder would like to show the major on the first round, and still have the option of rebidding to show an invitational hand. Transfers achieve this by getting opener to bid responder’s suit. That way the auction remains open and responder always gets the opportunity to bid again.
Responder bids two of the suit below their major. This is forcing and opener must complete the transfer by bidding two of partner’s suit.
Transfers are sometimes explained as simply a way to get the opening lead coming round to the 1NT opener. This is an incidental benefit – not the primary motivation.