RAM is the abbreviation for Random Access Memory, i.e. each memory cell can be recorded independent from the other memory cells. The structure is similar to a matrix pattern.
In most cases the main storage is the overestimated size of a PC. Besides the CPU the Random Access Memory is probably the most important component in a PC without which the data transfer would run much slower. Other types of memory are much slower. This is the reason why the data processing is nowadays running on the RAM memory modules as this kind of memory is much more rapid than others. The experienced PC specialists are saying "nothing will replace a Random Access Memory better than more Random Access Memory" and up to now this is true.
The RAM memory module needs to be provided with a certain voltage in order to be able to store data. The RAM controller is located on the so-called Northbridge chip set of the main board. The CPU can access the RAM memory module via the FSB (Front Side Bus). If the FSB has a higher speed, the performance of the PC will increase also.
The trend becomes apparent that important controllers are integrated on the CPU in order to avoid the detour via the circuit paths of the main board. The precursor for this is the new 64bit Athlon processor (independent from the manufacturer) where the RAM controller is already integrated.