I assume you're talking about room categories - generally refers to view and/or location at a particular
DVC resort. The Poly Island Tower or Bay Lake Tower would be good examples of this. Standard (or sometimes called resort view) will often be a low floor with a very basic view - could be of parking lot or a roof and sometimes you luck out with something that isn't really that bad (there are some BLT standard views that actually have views of theme park and fireworks, just on a low floor). Preferred is going to get you maybe a higher floor or view of the water/lake - at Poly I think it can be views of the golf course. Premium at those two resorts will be called "Theme Park" where you are guaranteed some sort of view of the Magic Kingdom and fireworks.
Of course, always best to do your research. I did an in-person tour with my guide at the Poly Island Tower 2 days ago. I mentioned to her some complaints about some of the room classifications, and she said she had heard that too and wouldn't be surprised if they re-categorize some of the rooms.