I'm sorry if the question is an easy one but my wife and I have not been frequent fliers for the last 6-7 years ... back when we were dating between two different countries

Flying LAX to ORD on Thursday ... Never checked in online before ahead of time.

1. Can we do this even if we are checking bags?
2. I read somewhere (can't find it now) that United has a special line/section for those who checked in online with bags. True?

Thanks in advance from a long time lurker.