A non-jump overcall: if an opponent opens 1♥, any of 1♠, 1NT, 2♣ and 2♦ from you are simple overcalls. If you make an overcall, it is usual to hold at least five card suits in your long suit, often six cards if the overcall is at the two level.
If the suit is good, you might overcall on a hand that is slightly too weak for an opening bid. For example with ♠K-Q-10-x-x and an ace on the side, it would be normal to overcall 1♠ over one of any other suit.