RAM, that means Random Access Memory, is a computer storage media that may be accessed faster than a hard disk drive, because the info 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 apps after they are executed, so the more RAM you can use, the more applications you'll be able to run simultaneously and the more people shall be able to look through your sites without any effect on the site’s/server’s general performance. Different from a disk drive, however, the RAM is employed for temporary storage purposes, since the info is lost once the power is shut off. When you use a shared web hosting account, the physical memory your scripts can use may be limited and may change according to what the some other clients on the same hosting server use. Through a virtual or a dedicated hosting server, alternatively, you'll have a set amount of RAM that will not be used by anybody else even when you don't use it at a particular time.