Answers

whoami

The answer to one of life's great questions and handy if you've forgotten who you are logged in as ! (This is actually quite useful in some UNIX programs called shell scripts.)

uname

Shows which version of UNIX is being used - for Condor it's a type of Linux

uptime

Displays how long the UNIX machine has been "up and running" for amongst other things (i.e. how long since it was last rebooted).