RAM is an abbreviation for Random Access Memory. This is a kind of computer memory, that, different from other storage devices such as hard disk drives or DVDs, enables the info to be accessed directly without reading the previous content located inside it. Each time a program is started, it's stored in the RAM, because it could be accessed much faster than if it was read from another media. With regards to the web hosting service itself, more RAM means that more web applications can work simultaneously on a particular hosting server, particularly when they are resource-demanding and are accessed by a great number of of people at the same time. Not like a shared web hosting package where the system resources of a particular account may be flexible and sometimes depend on what other end users consume also, a VPS provides a guaranteed amount of RAM which can be used at all times. That memory is allotted to one server only and will not be used by other customers even when it's not being used.