RAM is an abbreviation for Random Access Memory. This is a type of computer memory, that, different from other storage devices like hard disks or DVDs, enables the information to be accessed directly without reading the previous content stored in it. Anytime a program is launched, it's stored in the RAM, as it can be accessed much more quickly than if it was read from another media device. With regard to the web hosting service itself, additional RAM means that more web applications can operate simultaneously on a given web server, especially when they are resource-demanding and are accessed by a large amount of people simultaneously. In contrast to a shared web hosting plan in which the system resources of a given account can be flexible and often depend on what other end users consume too, a VPS has a guaranteed amount of RAM which you can use all the time. That memory is assigned to one server only and shall not be used by other customers even in case it's not used.