From the site:
"When cats walk or climb on your keyboard, they can enter random commands and data, damage your files, and even crash your computer. This can happen whether you are near the computer or have suddenly been called away from it.
PawSense is a software utility that helps protect your computer from cats. It quickly detects and blocks cat typing, and also helps train your cat to stay off the computer keyboard.
Every time your computer boots up, PawSense will automatically start up in the background to watch over your computer system.
Even while you use your other software, PawSense constantly monitors keyboard activity. PawSense analyzes keypress timings and combinations to distinguish cat typing from human typing. PawSense normally recognizes a cat on the keyboard within one or two pawsteps.
If a cat gets on the keyboard, PawSense makes a sound that annoys cats.
This teaches your cat that getting on the keyboard is bad even if humans aren't watching.
Once a cat has been recognized, PawSense blocks the cat's keyboard input. This keeps the cat from entering lots of commands to your programs or operating system...."