3 says either Bad hand Bad suit or Good hand Good suit. 3 asks which, with bad-bad opener bids 3, with good-good opener bids 3NT if balanced or 3 of other major with a singleton somewhere. 3NT asks for the singleton
3 is Good hand Bad suit or 6-4 with either 4 card minor. 3 asks which hand. Opener bids 4 card minor or 3 [singleton somewhere..3NT asks where] or 3NT [balanced]
3 shows 6-4 in the majors.
Responder bids 4 to agree hearts are trump or 4 to agree spades
3 shows good suit bad hand
3NT shows solid trump suit
4x new suit shows 6-5 shape
2 - 2NT
3 says either Bad hand Bad suit or Good hand Good suit. 3 asks which. With bad-bad Opener bids 3. With good-good opener bids 3NT if balanced or 3 of other major with a singleton somewhere. 3NT asks for the singleton
3 is good hand bad suit or 6-4 with either 4 card minor. 3 asks which hand. Opener bids 4 card minor or 3 [singleton somewhere..3NT asks where] or 3NT [balanced]
3 shows good suit bad hand
3 shows 6-4 in the majors.
Responder bids 4 to agree hearts are trump or 4 to agree spades
3NT shows solid trump suit
4x new suit shows 6-5 shape. If you opened 2 with five spades jump to 4 over 2NT to show this.