IonCube is a way of 'encoding' your scripts so they can be run as normal, but not read by whoever has it. See more at www.ioncube.com
it is a PHP encoder. lot of script developers encode their scripts with ioncube to keep the source closed. once the script is ioncube encrypted, your server needs to support ioncube for you to be able to install the script on your server. http://en.wikipedia.org/wiki/IonCube