2♣ does not promise 6, but if only 5 must have 4 card major
2♦ = 4=4=1=5 less one
1♣ = 17+ balanced, can be less if unbalanced
If your response structure makes one call a standout please share
e.g. if you play canape you can open 1♣ and rebid 1♥ if partner bids 1♦ or
if you play Kokish you might consider a 1♥ rebid because you can show a round two-suiter with your rebid
Plus... it's free!