RAM is an abbreviation for Random Access Memory. This is a sort of computer memory, which, unlike other storage devices like hard disks or DVDs, enables the data to be accessed directly without reading the previous content located within it. Whenever an app is started, it's stored in the RAM, because it may be accessed much faster than if it was read from another media. In terms of the website hosting service itself, additional RAM means that more web apps can run at the same time on a given web server, particularly when they are resource-demanding and are accessed by a great number of of people concurrently. Different from a shared web hosting solution where the resources of a certain account could be flexible and frequently depend on what other end users consume too, a VPS has a guaranteed amount of RAM you can use at all times. That memory is assigned to one hosting server only and shall not be used by other clients even if it's not being used.