What is it?
Windows Task Manager

What does it do?
This is the application that comes up in windowsk 2k/xp/2k3 when you hit Ctrl+Alt+Del together. This is used for ending applications and processes that are either no longer responding.

The other thing that this is good for is probably what brought you to this site Basically you can get a list of ALL processes running and if you were doing a search for taskmgr.exe then you already know what this screen looks like so I won't bother posting an image of it.

Search MS for more info: Link

Virus Precaution:
The original file from Microsoft gets placed in the C:WINDOWSSystem32 directory. if you find it anywhere else then you should be suspicious for sure.

You'll want to keep an eye on this google search for any known viruses. Currently there've been 0 reports. Everything in that search isn't related to this particular file.