ASAP is an acronym that stands for "As Soon As Possible". Some choose to spell it out, others tend to pronounce it "aysap", and I for one try to steer clear of it and other acronyms alltogether.

If you want something done and that something is urgent, requiring it to be accomplished quickly; then you want it done ASAP.

Variations on the original "As Soon As Possible" include:

ASAHP - As soon as humanly possible

ASAYC - As soon as you can

These tend to be a little more wimpy than the straight ASAP.

ASAP is a comparatively deferential expression, implying as it does that although you would like something done, there's no deadline so absolute that it can't be extended for a while if your interlocutor's house is on fire, or its grandmother died, or its hair needs washing, or Boston Kreme Donuts are on special offer TODAY ONLY!!!.

So for those occasions when "As Soon As Possible" just doesn't seem urgent enough, or simply to impress your friends (or intimidate your subordinates) with your erudition, you should specify that it abbreviates "Aut Statim Aut Prius" (roughly translated, that's "immediately if not sooner.")