Runes or runic is the name given to the ancient Norse alphabet. The script is also known as futhark or fuþark in the Norse language - a name which comes from the first few letters, a bit like the name "abc" in modern English. The study of runes is known as "runology".
The ultimate origins of runic are unknown, but the script is related to the Roman and Greek alphabets. Ancient Germanic tribes probably came in contact with these scripts, and brought them northwards. Rune stones are very common within Scandinavia, and can be found from Greenland in the west to Russia in the east. All of the Shetlandic examples are carved in stone, but runes were also inscribed on wood, and used on paper/vellum.
There are approximately 50 recognise runic inscriptions from Orkney and Shetland combined. It is uncertain whether the ones in Shetland are carved by natives, or by people visiting from Scandinavia.  
There is some pretty good evidence that runes were being used until the 15th century, in the Nordic countries, certainly in Iceland, Norway and Sweden. It is possible - although not proven - that this was the case in Shetland too. However, the Roman alphabet had been brought by Christian missionaries to the Norse several centuries before, and eventually outcompeted it.
In the 20th and 21st centuries, there has been some revival of the script, by groups as diverse as neo-pagans, and the Nazi movement. Some people use runes for divination, and it is also possible to get runic fonts for a computer.
- Ogham, a Pictish script, sometimes mistakenly referred to as "runes".
- Rune stone
- Michael P. Barnes
- Norn language
- Eth, thorn and yogh
- Page, R.I. Runes (University of California Press (June 9, 1987) - ISBN: 0520061144 )