RAM - Random Access Memory, or just "memory". RAM is the working scratchpad memory the computer uses to store code and data that are being actively used. RAM is effectively a storage area of bytes under the control of the CPU. RAM is relatively fast and able to retrieve the value of any particular byte in a few nanoseconds (1 nanosecond is 1 billionth of a second). The other main feature of RAM is that it only keeps its state so long as it is supplied with power -- RAM is not "persistent" storage.
CPU - Central Processing Unit - inevitably referred to as the "brains" of the computers. The CPU does the active "running" of code, manipulating data, while the other components have a more passive role, such as storing data. When we say that a computer can "add two numbers, a billion times a second" .. that's the CPU. When you hit the Run button, the CPU ultimately "runs" your code. Later on, we will complete the picture of how your Javascript code is run by the CPU.
