RAM, that is short for Random Access Memory, is a computer storage media which can be accessed considerably faster than a hard drive, as the data can be read randomly, skipping the bytes before the needed info is reached. On a server, the RAM is used to load scripts and web applications after they are executed, so the more RAM you are able to use, the more applications you'll be able to run simultaneously and the more people will be able to look through your sites with no effect on the site’s/server’s general performance. In contrast to a disk drive, however, the RAM is used for short-term storage purposes, because the information is lost as soon as the power is shut off. When you use a shared web hosting account, the physical memory that your scripts can use may be limited and could change based upon what the some other clients on the same machine use. Using a virtual or a dedicated web server, on the other hand, you'll have a fixed amount of RAM which won't be used by others even when you don't use it at a particular time.