As a beginner, I hears the terms "mil spec" (for "military specification) and "match grade" tossed about as indicators of handgun and rifle quality.  Everybody is an expert in the gun world, but I did gleen these differences between "Mil Spec" and "Match Grade" quality":

Match Grade quality

I'm told that an ordinary Wal-Mart gun parts are milled to a "loose" tolerance (gap between moving parts) at 1/15,000 of an inch, while a match grade weapon is milled to less then 1/1,000, a 15x closer tolerance.  The tighter parts, in turn, make the gun more accurate and shoot tighter groupings.

Mil Spec quality

Military spec is built for durability, not necessarily high accuracy (close enough for government work).  The idea is all about combat quality and durability.

For an example of there mil spec is not compatible with match grade, consider the AR-15 and M-14 AR triggers.

They are very hard and durable, but not too great for shooting matches.  You can tweak the spring to make is less poundage, or better still, drop-in a 3 pound AR competition trigger, like the AR Gold from American Trigger Corporation. (WARNING:  This AR trigger DOES NOT work on the Colt AR-15's because of the different pin sizes.)