In a way, the TLB acts like real memory while the main memory acts like virtual memory! The TLB is tiny while the main memory is huge, so the spill-over is kept in main memory. In the larger sense, real memory is where we store stuff that we are only working on right now, while disk is the much more gigantic memory where we keep all the items we ever will need.

The speed of access differs among these various systems, along with their size of storage, so that very fast memories tend to be very small, and very large memories (such as disk drives) tend to be very slow, able to hold billions of bytes of information.

A good analogy is an office. There is usually a desk to work at, to spread out one's papers while working. One or more filing cabinets are nearby where a vaster amount of papers is stored. If one needs a paper that is not on the desktop, he or she goes to the filing cabinet, finds it and puts it onto the desktop. Of course, she or he had better put some papers back into the filing cabinet sooner or later, or the desk will begin to look like a mountain range.