Buying wheel rims

What's the difference between 'disc rims' and just plain rims?

E.G.

http://www.chainreactioncycles.com/M...x?ModelID=3445
http://www.chainreactioncycles.com/M...x?ModelID=3444

Disc rims only work for disk brakes.
Plain rims can work with normal brakes (V-Brake) or disk brakes.

Thanks.