RAM is an abbreviation for Random Access Memory. This is a kind of computer memory, which, different from other storage devices including hard disk drives or DVDs, enables the data to be accessed directly without reading the previous content stored in it. Whenever a program is launched, it's stored in the RAM, as it may be accessed much faster than if it was read from another media. With regard to the web hosting service itself, additional RAM means that more web apps can work at the same time on a given server, especially when they're resource-demanding and are accessed by a large amount of people at the same time. Unlike a shared web hosting solution in which the system resources of a certain account may be flexible and often depend on what other end users consume too, a VPS offers a guaranteed amount of RAM which you can use all the time. That memory is allocated to one web server only and shall not be used by other clients even in case it is not used.