Runes were a means of recording information onto hard surfaces, such as metal, stone or horn. For simplicity of form and production, they tended to be made up of straight lines, rather then curves. The basic runes -- the Futhark (so called because these 7 letters 'led off' the remainder) -- all have in common a root in a single vertical stroke, with angular strokes (conventionally at about 60 and 120 degrees to the vertical) coming off it, on one side or both. A second vertical line may also appear parallel to the first connecting some or all of the angular strokes, and in later development certain angular strokes more closely approached the perpendicular position.
The runes were mythically supposed to have been learned by the Norse god Odin, whilst he hung upon the World-tree. They were suppsed to have magical powers in addition to their use in recording or transmitting information -- they could imbue an object with powers, and could be used, properly carved, to detect poison, lies or an enemy. Properly deployed they could also invoke a curse or confer a blessing.