RAM is an abbreviation for Random Access Memory. This is a sort of computer memory, which, in contrast to other storage devices such as harddrives or DVDs, allows the data to be accessed directly without reading the previous content stored within it. Each time a program is started, it's stored within the RAM, due to the fact that it can be accessed much faster than if it was read from another media device. With regard to the hosting service itself, more RAM means that more web applications can run concurrently on a certain web server, particularly if they're resource-demanding and are accessed by a large amount of people simultaneously. Unlike a shared web hosting solution in which the resources of a certain account can be flexible and often depend on what other users consume also, a VPS offers a guaranteed amount of RAM which you can use at all times. That memory is allotted to one web server only and won't be used by other customers even when it is not used.