When we open 2♣ and 2NT, we are showing very strong hands. These bids will handle the hands that are too strong to open at the 1 level.
A 2♣ opening is reserved for very strong hands. It does not say anything about clubs, meaning that it is an artificial bid. You can bid 2♣ with hands that have 8 clubs, or hands that have 0 clubs!
Need 22+ points
Any shape is allowed
You can also bid 2♣ with 9+ tricks in your own hand (such as having ♠AKQJT987 and ♥A)
Responding to 2♣:
Because opener has not shown anything about his suits, the partnership needs to conserve bidding room to give opener the most space to describe his hand.
Responder almost always bids an artificial 2D. This shows nothing about diamonds and is just a way to give opener the most room to bid out their hand.
Bids after 2D are usually natural and the partnership tries to find the best contract (usually game because of how strong the 2♣ opener is).
Examples of 2♣ opener
(Hand containing ~9 tricks)
Opening 2NT is very similar to opening 1NT. The only difference is that it requires more points.
Exactly 20-21 HCP
Balanced hand (No singleton or void, no more than 1 doubleton. In other words, 4-3-3-3, 4-4-3-2, or 5-3-3-2)
Examples of 2NT Opener:
(20 HCP and balanced)
(21 HCP and balanced)
One thing to keep in mind is that if your partner opens anything that isn’t 2♣, he cannot have 22+ HCP! This means that all of his 1 level openings can have at most 21 HCP.
Also remember that if your partner does not open 2NT, he will not have 20-21 HCP and a balanced hand. This completes the “ladder” of how to open balanced hands:
12-14: open at the 1 level and rebid 1NT
15-17: open 1NT
18-19: open at the 1 level and rebid 2NT
20-21: open 2NT