Bluetooth is a wireless standard that works over short distances.
As it happens, the standard is named after King Harald Bluetooth, because one of its authors was into Scandinavia and runestones at the time.
The Bluetooth sign is Harald's initials joined together (ᚼ + ᛒ). It's symmetrical. Take a vertical line and divide it into 5 equal parts, then put dots at the same distance to the left and right of the line at the ⅕ and ⅘ levels. All that's left is to connect the lines to get the Bluetooth sign.
The sign is usually drawn white on a blue background.