This program lets you easily install small updates / nightly updates to your ROM (supports specific roms.). For instance. Today I opened it up and it said there was an update to my nightly Cyanogen rom (There is usually one ever day). I clicked update and it downloaded a 9mb update. Rebooted the phone, installed it and then booted back up.
Just remember that when you first open the program up you have to point it to the ROM zip that you installed on your phone so it can analyze it to let you know if there are any updates