RAM is an abbreviation for Random Access Memory. This is a sort of computer memory, which, unlike other storage devices including harddrives or DVDs, allows the information to be accessed directly without reading the previous content located in it. Anytime a program is started, it's stored within the RAM, as it could be accessed considerably quicker than if it was read from another media. With regard to the web hosting service itself, more RAM means that more web applications can run concurrently on a given hosting server, especially if they're resource-demanding and are accessed by a large amount of people at the same time. Different from a shared web hosting plan in which the system resources of a certain account could be flexible and often depend on what other end users consume also, a VPS includes a guaranteed amount of RAM that can be used all the time. That memory is allotted to one server only and will not be used by other clients even when it's not used.