After a 2♦️ response to the 2♣️ enquiry, a further enquiry bid of 3♦️ asks about three-card major suits. In reply, 3❤️ shows three hearts while 3♠️ shows three spades.

Some people play that opener has two further options, to bid 3NT with 2-2 in the majors or 4♣️ with 3-3 in the majors.