Gigahertz is a measurement in chip performance that's expressed as billions of cycles per second. 1 GHz is the same measurement as 1000 MHz. Having a 1 GHz processor does not necessarily mean your computer will run faster, it means you can run more intensive programs with it. RAM temporarily stores information inside a computer. If you turn off your computer without saving the information, the contents will disappear.
RAM works like a whiteboard that is constantly overwritten with new data.
After you create a document, for example, you save it to disk. Your disk drive provides long-term storage for your document. When you access the document again, you open it back into memory from disk. When the document is in memory, the CPU can work over the information. The amount of memory your computer needs depends mostly on the requirements of the software programs you run.