RAM (Random Acces Memory) is a please into computer where applications and date are stored so it can be quickly reached by processor. A RAM is much faster to read from and write than any other componennt in the computer such as Hard Drive, Cd or USB flash drive.
RAM speeds are veritable, usually the speed are written down on the packaging. It could say 1333MHz,1600MHz or even faster RAM it could be up to 2800MHz due my research. You also need to look at the latency. If the CL numbers are higher then ram could not be thats fast if the CL nuber are lower agh the same speed.
So if you decide to purchase any RAM for your computer/laptop I would recommend do a little research what out there now, make sure to compare speed with other same range rams and you the best for the value.