This is another one that perhaps should not be called a Convention. It functions more as a modification to your basic bidding system.

In fact, when you play 2/1 the majority of your bids keep the exact same meaning that they always did. There are just two changes.

In standard bidding, when partner opens 1 of a suit and you respond at the 2-level (not jumping) with a new suit you are required to have at least 11 points.
Playing 2/1 you are required to have at least 13 points and the bid is game-forcing.
These are the ONLY sequences that the 2/1 Game Force applies to:

OpnrResp     OpnrResp     OpnrResp     OpnrResp     OpnrResp     OpnrResp
 1♠ 2      1♠ 2      1♠ 2♣      1 2      1 2♣      1 2♣

In these sequences, the fact that they are now forcing to game rather than just forcing for one round, changes the complexion of the bidding rather dramatically. With both partners knowing that they cannot stop until a game contract is reached, jump bids can be avoided and more information can be exchanged at a lower level. Using 2/1 probably doesn't enhance your game bidding very much, but it makes a great difference in slam going hands.

There were TWO differences, remember? The second one is in how you handle those 11 and 12 point responding hands where you WOULD have bid 2 of a new suit and now you are not allowed to. The solution is that you change your 1NT response range. In standard bidding a 1NT response shows 6-10 points. In 2/1 it shows 6-12 points and it is forcing for 1 round.

This is just a snapshot, if you intend to play 2/1 you need a lot more.
Lesson available on BakerBridge.