You are South and you hold this hand:
Your partner has bid 1S. As this is a minimum bid (at the one level) your partner could have a weak hand.
The bidding has gone as follows:
It is unlikely that your partner holds more than 8 or 9 points, otherwise he would have made a bid at the 2 level. You know that you are unlikely to hold more than 24 points between you, fewer than the 25 points generally needed to bid for game. You should just do a single raise to the 2 level, which tells your partner that you don’t have enough points between you to bid for game.