intel macs, rosetta, and programs ?'s

I dont fully understand how the intel mac os works. If your running office say, its running under the rosetta emulater? Also if i buy office for the mac will i get a free upgrade to the universal application? Will it run the same under the emulator? Will i have to do anything special to get it to run? Im about to buy a new mac but want to make sure I wont have any problems especially with powerpoint, word and excel.

Thanks