What's RAM

Random access memory (RAM) is a type of computer storage whose contents can be accessed in a fixed time does not care where the data in memory. This contrasts with the serial memory devices, such as magnetic tapes, disks and drums, in which the mechanical movement of the storage media to force the computer to access data sequentially. First time in 60'an known. Only when the semiconductor memory that has not been popular because the price is very expensive. When it is more common to use magnetic main memory. Companies like Intel's semiconductor producing debut with RAM, more precisely, DRAM types.

Usually RAM can be written and read, contrary to (read-only-memory, ROM), RAM is usually used to strorage data (main memory) for use in computers and change the information on, although some tools use some kind of RAM to provide a secondary storage long-term. But there is also an opinion that the ROM is another type of RAM, because it is actually also Random Access as well as SRAM or DRAM. It's just that indeed the process of writing the ROM does not require a specific process as easy and flexible as well as in the SRAM or DRAM. Also addresses some part of the space of RAM (main memory) of a system that is mapped into one or two chip ROM.

(Wikipedia)