The first two are right. The last bit about cams is wrong... I wouldn't waste my time on cams.
I'm talking about dvds. Some people get dvd screeners. For those who don't know what a dvd screener is, it's a pre retail dvd, sent to rental stores, and various other places (eg. reviewers) for promotional use. They usually don't have the special features of the retail version of the dvd. This has been going on back in the VHS days and still continues. My brother would get VHS screeners when he worked at a video shop and I would watch movies before they were released.
Also, some dvds are released in different dvd zones before other zones. So, you can get a copy of a dvd from one region before it hits the cinema in your own region. Again, nothing has changed as people have been getting copies of dvds from different zones since dvds came out.