RAM is an abbreviation for Random Access Memory. This is a sort of computer memory, which, different from other storage devices like hard disk drives or DVDs, enables the info to be accessed directly without reading the previous content saved in it. Whenever an application is launched, it is stored within the RAM, since it can be accessed much more quickly than if it was read from another media device. With regards to the hosting service itself, more RAM means that more web applications can run at the same time on a particular server, especially if they're resource-demanding and are accessed by a large amount of people all at once. Different from a shared web hosting solution in which the system resources of a certain account can be flexible and often depend on what other end users consume also, a VPS provides a guaranteed amount of RAM which you can use always. That memory is allocated to one server only and shall not be used by other clients even in case it's not used.