In the old days with film cameras they were invariably sold with a 50mm standard lens of some sort. This was because the field of view from a 50mm lens roughly equates (apparently) to a similar field of view to our eyes.
Fast forward a couple of decades to today, and that 50mm lens on your 1.5x DX crop sensor now acts like a short telephoto I.e. Approx 75mm. Therefore, by putting a 35mm lens on your crop sensor, it behaves (or at least has a similar field of view) to a 50mm again (35 x 1.5 crop). It's a better general purposes lens for a DX camera, as it will enable a slightly wider view.
It's still not really a wide angle though. We old photographers used to class a 28mm as the start of real wide angle, and that would equate to approx an 18mm lens today.