2D and SDS-PAGE.... - SDS is the only difference? (Feb/15/2006 )

i think soon enough noone will answer to my questions since they are so so basic and stupid....but sometimes you just cant find simple and straight forward answers on the web.. please explain to me the differences of 2D and SDS-PAGE?

Most simple explanation I can imagine:
SDS-PAGE separates proteins by their molecular weight.
2D in first dimension separates by isoelectric point (IEF) and then in second dimension by molecular weight (SDS-PAGE).

The first separation is on a native gel (with a Ph gradient established). It does not include SDS.
The second separation is on a denaturing gel, witch contains SDS.