RAM is an abbreviation for Random Access Memory. This is a kind of computer memory, that, different from other storage devices such as harddrives or DVDs, permits the information to be accessed directly without reading the previous content stored inside it. Anytime a program is started, it is stored inside the RAM, since it can be accessed much faster than if it was read from another media. With regard to the website hosting service itself, extra RAM means that more web apps can work concurrently on a particular web server, particularly when they're resource-demanding and are accessed by a significant number of people at the same time. Different from a shared web hosting package in which the resources of a given account could be flexible and quite often depend on what other users consume as well, a VPS has a guaranteed amount of RAM you can use always. That memory is allotted to one server only and will not be used by other customers even if it's not used.