Well, it's not the best word to describe it, but it's close enough. Stance moves mean that the character is put into a specific state. Characters like MvC3 Jill, Litchi, and Xiaoyu will assume a certain position. Others like Guy, El Fuerte, and She-Hulk do theirs in a run and characters like Vega and Gen do theirs in a pseudo wall jump. Regardless of the "stance", what they can do in this position varies as per character design. The one thing they have in common is that there are followup attacks. These aren't the same as built in combos though. For example, with El Fuerte, from his run, he has several options to choose from and the opponent is forced to guess which attack El Fuerte will use as if the opponent guesses wrong, he gets punished. For the most part, stance moves act as mixup setups, but can also be combo extenders depending on the character.