RAM is an abbreviation for Random Access Memory. This is a sort of computer memory, that, different from other storage devices such as hard disk drives or DVDs, allows the information to be accessed directly without reading the previous content located in it. Anytime an application is started, it's stored in the RAM, since it could be accessed much more quickly than if it was read from another media device. With regard to the hosting service itself, extra RAM means that more web apps can run simultaneously on a certain web server, particularly if they're resource-demanding and are accessed by a significant number of people concurrently. Unlike a shared web hosting solution where the system resources of a certain account can be flexible and often depend on what other users consume as well, a VPS provides a guaranteed amount of RAM which you can use always. That memory is allotted to one web server only and will not be used by other customers even when it's not used.