@ossobucotemp,
It is a spy program that the antagonist installs on your computer without your knowledge. It records every key you type and sends it to the villain who then (seeing every key you typed) knows your passwords and your web history at which point they have access to all of your accounts. It is one of the reasons that you shouldn't use public computers.
Nasty stuff (and pretty common in the hacker biz). A computer savvy individual with physical access to your computer can install one with relative ease.