RAM is an abbreviation for Random Access Memory. This is a kind of computer memory, which, in contrast to other storage devices like harddrives or DVDs, enables the information to be accessed directly without reading the previous content stored inside it. Each time a program is launched, it's stored within the RAM, because it could be accessed considerably quicker than if it was read from another media device. With regard to the web hosting service itself, extra RAM means that more web apps can run concurrently on a particular web server, especially if they're resource-demanding and are accessed by a large number of people at the same time. Not like a shared web hosting plan where the resources of a given account can be flexible and frequently depend on what other users consume also, a VPS has a guaranteed amount of RAM you can use at all times. That memory is assigned to one hosting server only and will not be used by other customers even in case it is not used.