RAM is an abbreviation for Random Access Memory. This is a kind of computer memory, that, different from other storage devices like harddrives or DVDs, allows the data to be accessed directly without reading the previous content saved within it. Anytime a program is started, it is stored within the RAM, because it can be accessed considerably faster than if it was read from another media. In terms of the web hosting service itself, more RAM means that more web apps can work at the same time on a certain hosting server, particularly if they're resource-demanding and are accessed by a large amount of people simultaneously. Different from a shared web hosting solution where the resources of a certain account can be flexible and quite often depend on what other end users consume also, a VPS includes a guaranteed amount of RAM you can use always. That memory is allotted to one web server only and won't be used by other customers even if it's not in use.