I find using analogies the best way to do it. For example, explaining the difference between RAM and a hard disk. I tell people to imagine they are doing research for a project. They go to the library to get said research. The shelves of the library is the hard drive, the study desk is your RAM and the dewey decimal system is like the MFT.

This particular analogy helps me explain what RAM is, how it works, why computers speed up with more of it. What a HDD is. what defrag is and how it works. The difference between quick and full formatting. Probably more things I can't think of right now!