The origin of runes is shrouded in legend. As rune-roots are of Norse mythology and history, so is the legend. Odin, a god, hung for nine nights on The Tree Of The World. He is shown as 'The Hanged Man' in the tarot in many decks, depending on the artist's attention to detail, and the theme of the overall deck. Just before he fell, he grabbed the symbols, and this sacrifice is how humanity was given runes. This is one of the theories behind why rune tablets are generally either wood or stone; these materials are attuned to nature and the forest, where Odin was when the runes were 'born'.
There are either 24 or 25 runes in a set, depending on who you ask. There is some debate about whether or not the Blank Rune should exist in a set, (further details under the rune's meaning) but I personally use all 25. A 'Blank Rune' to me, is like a space in written text. It may not be a part of the alphabet in the traditional sense, but a space is vital in understanding written language. And I believe that having all the possible runes in my set is just as vital to further my understanding and interpretation of a runecasting. Otherwise, it would be like a novice taking the 'Death' card out of the Tarot deck to ensure it wouldn't appear during a tarot reading, never realizing that 'Death' doesn't actually mean 'Hope you filled out your will correctly' but that it represents a change of some kind.
All the information in my Runes section is derived from a few sources, the most important being Lisa Peschel's book A Practical Guide to The Runes: Their Uses in Divination and Magick. There are so many different research materials I could have used, but I found that Peschel's book was the most direct, down-to-earth approach.
There a runic alphabets (futharks) as well, in case you've ever seen text written in runic script. There are several futharks, Anglo-Saxon, Younger... but I prefer to respect my Elder. But you may notice some differences if you are using a different futhark. Likewise, the sequencing of runes tends to vary, even in my research alone, but the order I've chosen is the traditional sequence. Don't panic if you find another sequence in a book you may have picked up. Just go with what feels right.
The purpose of runecasting is for divination, or guidance - similar to the ideology of the Tarot. There are several different layouts, meanings, interpretations and jargon, which I will try to break out into separate sections to make it easier.