Swivel/Flex/Universal sockets, I have heard them called all 3. I put together a mix-matched SAE and Metric sets for myself. I will say that they are probably about the most useful purchase I have ever made. Sometimes a regular socket and universal adapter just won't fit in the confined space (too long) and these sockets work well for that. 3/8 drive seems to be the most useful drive size for them although I have seen some in 1/2 drive. 1/4 drive just didn't have all of the sizes I wanted.
Now as to what brands work best? Hard to say, there are a lot of good choices out there. The Craftsman ones work just fine. I like Mac and Proto because they have allen screws in the joints that you can tighten if needed. Snap On ones seem to have the best clearance and can work at more extreme angles. I have both 6 point and 12 point sockets. There are times when the 12 point sockets make access even easier, especially when it's hard to first get the socket on the bolt. Any way you look at it, when you really need that type of socket, there are few other tools that will work in that situation.