RAM, which is short for Random Access Memory, is a computer storage media which can be accessed way quicker than a hard disk, simply because the info can be read randomly, skipping the bytes before the needed information is reached. On a server, the RAM is used to load scripts and web programs after they are executed, so the more RAM you can use, the more programs you'll be able to run simultaneously and the more people will be able to browse your sites with no effect on the site’s/server’s overall performance. Unlike a disk drive, however, the RAM is employed for momentary storage purposes, since the data is lost as soon as the power is shut off. In case you use a shared web hosting account, the physical memory which your scripts may use may be limited and may change according to what the other customers on the same server use. With a virtual or a dedicated hosting server, alternatively, you will have a fixed amount of RAM which won't be used by anybody else even if you do not use it at a given time.