RAM, that is short for Random Access Memory, is a computer storage media which can be accessed considerably faster than a disk drive, as the info can be read randomly, skipping the bytes before the needed data is reached. On a web server, the RAM is used to load scripts and web applications once they are executed, so the more RAM you can use, the more apps you'll be able to run at the same time and the more people will be able to browse your sites without effect on the site’s/server’s overall performance. In contrast to a disk drive, however, the RAM is used for short-term storage purposes, as the info is lost the moment the power is shut off. When you use a shared web hosting account, the physical memory which your scripts could use may be limited and might change based on what the other customers on the same hosting server use. Through a virtual or a dedicated web server, however, you'll have a set amount of RAM which will not be used by anyone else even if you do not use it at a given time.