RAM is an abbreviation for Random Access Memory. This is a type of computer memory, which, in contrast to other storage devices such as harddrives or DVDs, allows the info to be accessed directly without reading the previous content saved within it. Every time an app is started, it's stored in the RAM, because it may be accessed considerably faster than if it was read from another media device. With regards to the hosting service itself, more RAM means that more web apps can operate simultaneously on a particular web server, especially when they're resource-demanding and are accessed by a significant number of people all at once. Unlike a shared web hosting plan in which the resources of a certain account could be flexible and often depend on what other users consume too, a VPS provides a guaranteed amount of RAM which can be used all the time. That memory is allocated to one web server only and won't be used by other clients even when it's not in use.