No...Mashing is the conversion of the starch in the grain to sugar through the application of heat and time...It's an actual chemical reaction.
Steeping is just that, getting some color and flavor from the grain, like steeping tea bags, most of the grains we steep don't convert on their own, they need a base grain like two row to help convert.
Start here and read on into the allgain section. http://www.howtobrew.com/section2/index.html
And here's some info on steeping http://www.howtobrew.com/section2/chapter13.html
There is a midway between Extract with steeping grain, and all grain and that's called Partial Mashing. do a search and you will find plenty of info.