IonCube Loader is a tool, that's needed to run files which are encoded with ionCube PHP Encoder. The latter is an application used to make PHP code human unreadable, to protect it from reverse engineering and / or not authorized usage. A large number of script-driven apps, in particular discussion boards, content management systems and e-commerce solutions are encoded with ionCube PHP Encoder, which means that if you obtain a script and you notice that ionCube is one of the website hosting environment requirements, you need to make sure that your hosting server has the instrument pre-installed. Although it is not that difficult to install it when you have your own server, it is almost impossible to do that on a shared web hosting server for the reason that the PHP environment should be precompiled and all of the clients on the server shall be affected.