When I make a Chinese-type marinade I use dry sherry. It's just a classic combo of:
sometimes a bit of pineapple juice depending on what "it" is
It's hard to say what "specifically" it's used for as it is in so many different dishes/recipes. It's used to give things that certain sweetness and taste once you use it you will say - "oh, that's what that flavor is".
When you say rice wine are you talking about saki? Or are you talking about rice wine vinegar? I just want to be sure.