Discrete and dedicated are the same thing, referring to graphics chips (ie not integrated). Not all dedicated cards will be good for gaming, but they should all be better than integrated.
As Candlebbq said, if you are looking at a laptop that uses duel video chips, that will be listed in the features. It is highly unlikely you would run into a manual switch, though. I'm about 4 months behind reading a computer magazine, and have not looked at any tech sites online for 5 or 6 months, and even then the first generation of devices that used a manual switch were outdated. It is only early adopters that are willing to put up with that inconvenience; once the first automated system came out manual switches became a hassle rather than a necessary step to enable a cool feature.
