<p>Does full trust mean the same as Run As Administrator?  I have read things stating that "for this to work, the application must be a full-trust application."  Is that the same as you must have administrator privileges to run the application?  If not, what's the difference?  How can you tell if an app is "full-trust"?</p>

<p>I am told that "Administrator or not, .Net apps won't do certain things if they aren't running from a 'trusted' location."  What is a "trusted location"?  If you run an app from a "trusted location", can you do things that "require full-trust" without being an administrator?</p>

No.  As of version 2.0, the .Net framework has it's own little filesystem setup for security.  Administrator or not, .Net apps won't do certain things if they aren't running from a 'trusted' location.
Just about anything on your local hard drive is trusted, but (and supposedly they fixed this for 3.5sp1) even the local intranet is
not
trusted, so most .Net desktop apps will fail to even start if they're sitting on a network drive or share.
You can change the configuration on a machine so it will allow apps from that zone, but it has to be done for
every
machine that's going to run the application, which breaks a common corporate deployment scenario.
From an ASP.Net standpoint, it also means that certain activities require more 'trust' than others.  Sending e-mail, for example, can cause exceptions if not set up correctly.