Normally, snowbikes are for downhill only. You take them on a ski lift to the top and make your way back down to the bottom and there is no pedaling involved. I have however, seen a snowbike adapted with a tractor style tread in the rear to pedal up as well.
While there are some variations that adapt normal bike frames to snowbikes, most snowbikes are made for the snow only.
Snowbikes have been around for a long time and have had some success, but they have never really caught on as a serious alternative to skiing/snowboarding.