RAM is an abbreviation for Random Access Memory. This is a type of computer memory, that, different from other storage devices including hard disk drives or DVDs, enables the data to be accessed directly without reading the previous content stored within it. Each time a program is launched, it's stored inside the RAM, due to the fact that it could be accessed considerably quicker than if it was read from another media. With regard to the web hosting service itself, additional RAM means that more web apps can run simultaneously on a certain hosting server, especially if they're resource-demanding and are accessed by a large number of people concurrently. Not like a shared web hosting package where the system resources of a given account may be flexible and frequently depend on what other users consume too, a VPS provides a guaranteed amount of RAM which you can use always. That memory is assigned to one hosting server only and won't be used by other clients even if it's not in use.