Its pretty much like y'all. Just addressing more than one person, although sometimes it sounds odd in places y'all would be okay. Like "Hi y'all" fine "Hi youse" not as.much. in place of that I'll just drop the youse or use something else. But I do use it alot still like "how.youse doing" or alot of the times if I want both my kids to do something I'll tell them ,"youse need to do (whatever)" or sometimes "youse two" it feels wierd typing it out because it's not something I ever use in text but it's just to me the plural form of you like cookies is more than one cookie youse is more than two people