RAM is an abbreviation for Random Access Memory. This is a sort of computer memory, which, different from other storage devices like hard disk drives or DVDs, permits the info to be accessed directly without reading the previous content saved in it. Whenever an application is launched, it is stored in the RAM, as it could be accessed much quicker than if it was read from another media. With regards to the web hosting service itself, more RAM means that more web applications can operate all at once on a given web server, especially when they are resource-demanding and are accessed by a large number of people at the same time. Not like a shared web hosting package where the system resources of a given account may be flexible and often depend on what other end users consume also, a VPS includes a guaranteed amount of RAM which you can use all the time. That memory is assigned to one web server only and will not be used by other customers even if it's not used.