Rugby Socks are a key part of the players attire. The modern socks tend to be synthetic material and at the higher level will offer a degree of protection to the feet from the weather. Both International and Club sides have their own colours and styles for socks. For instance England wear a black sock with white tops rather like the main sponsors of rugby a pint of Guinness, though England had this design before Guinness became involved.
Evolution of the rugby sock
The original socks would have been woollen walking socks. The first improvement was to mix wool with other fabrics like cotton. Then a mixture of wool and synthetics. The problem with these old socks was they were inclined to shrink if washed at to high a temperature and if the temperature was to low then they would become stained. The modern synthetic materials do not last any longer than the old ones but are not so susceptible to the elements.
Club socks are the norm at all levels of the game and of course the Barbarians famously wear their own club socks when playing for the side. The other main use for socks is to support the shin pads worn by forwards particularly the front row.