RAM is an abbreviation for Random Access Memory. This is a sort of computer memory, that, different from other storage devices such as harddrives or DVDs, enables the information to be accessed directly without reading the previous content located inside it. Every time an app is started, it's stored inside the RAM, due to the fact that it can be accessed much more quickly than if it was read from another media device. In terms of the web hosting service itself, more RAM means that more web apps can operate at the same time on a certain web server, especially if they're resource-demanding and are accessed by a great number of of people concurrently. Not like a shared web hosting package where the system resources of a particular account could be flexible and often depend on what other end users consume as well, a VPS offers a guaranteed amount of RAM which can be used at all times. That memory is allocated to one server only and won't be used by other clients even when it is not being used.