Can someone explain the different tackles used on fly rods?

From everything I've looked up, I see that there are a couple different kinds of tackle used for fly fishing, Line Backing, Line, leader, tippet, and i think that's it. For line backing, do you fill your entire spool with backing? half of the spool? would you put half backing/half line? and how strong should each be, for example, should the backing be stronger then the line, vice-versa, or should they just be the same? And finally, what are good backing/line brands? sorry for asking so many questions, I just really want to start fly fishing, to do something a little different from traditional spin tackle fishing.