RAM is an abbreviation for Random Access Memory. This is a kind of computer memory, that, in contrast to other storage devices including harddrives or DVDs, permits the info to be accessed directly without reading the previous content saved in it. Every time an application is launched, it's stored inside the RAM, as it can be accessed much more quickly than if it was read from another media. With regards to the hosting service itself, additional RAM means that more web apps can run all at once on a particular web server, particularly when they are resource-demanding and are accessed by a significant number of people all at once. Different from a shared web hosting package in which the system resources of a given account may be flexible and quite often depend on what other end users consume too, a VPS offers a guaranteed amount of RAM that can be used all the time. That memory is allotted to one server only and won't be used by other customers even in case it is not used.