RAM is an abbreviation for Random Access Memory. This is a sort of computer memory, which, different from 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 an application is launched, 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. With regards to the web hosting service itself, extra RAM means that more web apps can operate all at once on a given hosting server, especially when they're resource-demanding and are accessed by a large amount of people all at once. In contrast to a shared web hosting package in which the system resources of a particular account may be flexible and quite often depend on what other end users consume as well, a VPS provides a guaranteed amount of RAM you can use at all times. That memory is allocated to one server only and won't be used by other clients even if it's not being used.