What is an End Plate?
There are good introduction-to-house-wiring books available. Home centers often have these, or cover the basics in a chapter of their general home maintenance books. Your local public library is likely to have much more detailed books, or can order them for you via inter-library loan.

For the questions you're asking, it sounds like reading through one of those would be an excellent investment of your time and money.  Asking here's more useful when something needs clarification or you have a question that's more in the how-to range.