Possible meanings are 1) "song people sang while going up to Jerusalem for a celebration" or 2) "song people sang while going up the steps into the temple" or 3) "song whose words are like steps." See how you translated this in [Psalms 120:1](../120/001.md)
This is the beginning of a hypothetical statement about what would have happened if Yawheh did not help them. But Yahweh really was on their side. (See: [[rc://en/ta/man/translate/figs-hypo]])