Short answers, pulled from the story.
Younger Futhark is a runic alphabet used from about the 9th century in Scandinavia and Viking Age settlements abroad. It is a reduced form of the Elder Futhark with only 16 characters, down from the original 24.
The reduction was completed by the late 8th century, driven mainly by the loss of the written distinction between voiced and unvoiced consonants. A writing custom that avoided carving the same rune consecutively also erased the distinction between long and short vowels in written form.
Long-branch runes, associated with Denmark, were generally used for permanent inscriptions carved in stone. Short-twig runes, associated with Sweden and Norway, served everyday messages on wood. In the short-twig form, nine of the sixteen runes appear as simplified variants of the long-branch shapes.
Use declined after the Christianization of Scandinavia, and from the 12th century most Scandinavian writing shifted to the Latin alphabet. Medieval runes survived in use until around 1500, and the Dalecarlian runes, a descendant form from the Swedish province of Dalarna, remained in some use until 1910.
The Bryggen inscriptions are more than 600 runic texts discovered in Bergen since the 1950s, mostly carved into wooden sticks. They were written in medieval runes, a descendant of the Younger Futhark, and show that runes were in common use alongside the Latin alphabet for several centuries.
The Bluetooth logo is a bind rune combining the Younger Futhark characters hagall (H) and bjarkan (B), the initials of Harald Bluetooth, a tenth-century Danish king after whom the wireless technology was named.