There are many different types of RAM On the market, the different types being denoted by letters that are added to the acronym. Each of these different types of RAM has somewhat different characteristics than the others. In the most basic sense, the three types of RAM in usage today include static (SRAM), dynamic (DRAM) and phase-change (PRAM).
One of the most significant developments in RAM has been the advent of Solid State Drives (SSD). These drives function like RAM but lack the volatility that characterizes RAM. This mean that they can be used to store information such as operating systems, files and so forth and that, when the computer is shut down, that information remains available. They are much faster than standard hard drives, owing to the fact there are no platters from which the computer has to read.