Playing three weak twos, 2♣ is the only strong opening bid apart from 2NT.
Most of the team, responder relays to 2♦, awaiting more detail of opener's hand.
But there's one exception, and that's a response of 2♥/♠. There are two possible meanings, assuming the bid is natural:
responder has a good, 6-card suit, typically K Q J x x x or similar
responder has a weak hand including a 5+-card major, say Q x x x x and out. This response is non-forcing.
Having 'played' the former scheme for several years without the bid ever coming up, we've switched to the Mike-Bell-advocated latter approach.
Opener is now in control. He knows that responder will have nothing to offer outside his bid suit, so his rebid will almost certainly end proceedings. Without good, 3-card [or better] support for responder's suit, opener will probably rebid his own suit, and that will be that.