Generally speaking, everything from the first ? on is additional information used server side. What that information is exactly, who knows. I suspect a lot of it is tracking info.
When posting links to items on ebay, aliexpress, etc. It's best to just delete all that unnecessary stuff, if for no reason other than removing clutter from the post. Just whack off the first ? and everything after. It's a good idea to test that the link still goes where it should, but usually it does.