Runes are not only a powerful tool for divination, but also a form of alphabet that is present in nearly every culture. Runes are normally strongly associated with Norse paths and culture, however they are also found and influenced by Germanic, Pictish, Saxon, Slavic, Greek, and Gaellic cultures to name a few. For the sake of keeping this article within the basics level, I'm going to concentrate on the Nordic form of runes since they are what most are immediately drawn to and are familiar with. Other forms will be featured in other articles.
Nordic runes are symbols representing alphabets and have specific meanings. They are named after trees, animals, places of importance within the home, and after the gods themselves. Various aspects of Norse life was venerated within the runes. For instance, victory, death, the hearth, ice, and joy were all translated within the runes. Because of their connections with these things, they were often found on stone or wooden shrines, or markers to mark them as places of importance. To the Norse, passing the legends and lore of the gods and heroes were as important to them as to the Celts. So only the most important things were put into markers such as a shrine to the gods, a place of worship or other sort of ideology. In latter times, poems and legends were translated into written word using the runes. Between the 8th and 11th century a poem was discovered having 24 lines of poetry, each one naming a specific rune. The poem itself was outlawed as blasphemy and heresy in the 16th century and remained unseen until the middle 18th century. This set of 24 lines of poetry was called the Edda.
Runes are divided into two groups, Elder Futhark and the Younger Futhark. The Elder Futhark is the form that made up Old Norse or Proto Norse alphabets. It was made up of 24 alphabets and range from 2nd to the 8th century. It has been found on amulets, artifacts, tools, weapons, and as forms of divination that predate alphabet use from around 100BCE. The Younger Futhark evolved as the language evolved and less phonetics were needed. Therefore, instead of 24 runes, there were 16. It was roughly used from the 9th century and were finally used commonly around 800AD. Younger Futhark is divided into two types, long branch and short twig runes. Long branch runes were Danish descended and short twig were descended from Swedish and Norwegian runes. From the Younger Furthark, staveless runes called Halsinge Runes (named for the location they were discovered) developed and were used in every day life of sending official or private messages around 900 AD. Middle Age runes, which look more like a semi modern alphabet one could recognize, evolved around 1100 and Dalecarlian Runes (circa 1500) both evolved from the Younger Futhark.
Runes are divided into three Aetts or Eights. Each Aett is dedicated to a specific Norse god. The runes themselves were said to be given to humanity as a form of higher communication and as a form of magick and divination from the god Odin. As legend goes, Odin came upon the three Norns, sisters of Fate that wove the pasts, presents, and futures of humanity and gods alike. He inquired of their ability to know all of the secrets of the worlds and the universe and so he was referred to the giant Mimir. After pledging his left eye, Odin received a fraction of the knowledge he sought. But that was not enough and so he traveled to the World Tree where he hung for nice days and nine nights between the worlds and in doing so he acquired the knowledge of past, present and future. Giving these gifts to his ravens, he taught select women and some men the meaning and use of these symbols known as the runes. The Havam which is a section of the Edda, is Odin's words to humanity regarding how to use these runes and the wisdom he gleaned while hanging from the World Tree.
Runes were cast as a form of divination in stone, earthenware clay, animal bones, or wood. If they were cast in stone or clay they were referred to as rune stones. If they were on bone or wood they were referred to as runestaves. Runes were cast in two ways. They were either tossed onto the Earth or they were used with a pelt (some say a hare some say elk). In one writing the runes are said to be used on white cloth, although cloth was a precious commodity in those days.
From the writing "Germania" from Tacitus comes this example of how they were used:
"To divination and casting of lots, they pay attention beyond any other people. Their method of casting lots is a simple one: they cut a branch from a fruit-bearing tree and divide it into small pieces which they mark with certain distinctive signs and scatter at random onto a white cloth. Then, the priest of the community if the lots are consulted publicly, or the father of the family if it is done privately, after invoking the gods and with eyes raised to heaven, picks up three pieces, one at a time, and interprets them according to the signs previously marked upon them."
As a form of divination, they were used between 100 BC to 1600 AD. They were made illegal to use for divination purposes after this time. From then on, the runic alphabet evolved to resemble Latin alphabet likely in an attempt to not be charged with heresy.
The three Aetts are divided into 8 sections of runes. Freyr/Freya's Aett contain Fehu, Uruz, Thurisaz, Ansuz, Raido, Kenaz, Gebo, and Wunjo. They tend to involve knowledge of material goods, pleasure, health, strength, power, and gifts. In this case, the gift is seen as a sacrifice or something that is offered willingly in order to create a balanced situation.
Heimdall's Aett consisted of Hagalaz, Nauthiz, Isa, Jera, Eihwaz, Perthro, Algiz, and Sowillo. These deal with the force and power of nature, of the mind, of protection and honor, peace and harvest.
The last Aett is Tyr's Aett. They consist of Tiwaz, Berkano, Ehwaz, Mannaz, Laguz, Ingwaz, Dagaz, Othala.
Note there is no historical support for the more modern addition of the blank rune. By definition, runes are symbols and a blank rune has no symbol. The blank rune is also sometimes referred to as the Wyrd rune or Odin rune. The blank rune was not introduced until around 1980 with Ralph Bum's Book of Runes. Many consider this to be a woefully inaccurate reference despite it's popularity. In some forms a reversed or merkstave rune may be read as it is cast in a reversed postion. It may be read as a more negative meaning of the original meaning of the rune. The runes themselves are translated in accordance to the way they are cast and the runes near them.