RAM is an abbreviation for Random Access Memory. This is a type of computer memory, that, different from other storage devices such as harddrives or DVDs, enables the info to be accessed directly without reading the previous content located within it. Every time a program is started, it's stored inside the RAM, because it may be accessed much more quickly than if it was read from another media. In terms of the website hosting service itself, additional RAM means that more web applications can run at the same time on a given server, especially if they're resource-demanding and are accessed by a significant number of people at the same time. Unlike a shared web hosting package where the system resources of a certain account could be flexible and often depend on what other end users consume also, a VPS provides a guaranteed amount of RAM which you can use always. That memory is allocated to one hosting server only and will not be used by other customers even if it's not used.