In Game of Thrones the Wall is the huge stretch of magical ice that separates the Seven Kingdoms from the wild lands beyond. Lands that harbor giants, the Night King and the White Walkers, and their army of reanimated corpses known as the wights.
George RR Martin took inspiration for the Wall from Hadrian's Wall in England, which was built by the Romans as a defensive fortification. In GoT the Wall is also a line of defence, but it's not just the wall—it's the gatekeepers of it too, the Night's Watch.
Inspired by such real-world orders as the Knights Templar, the Night's Watch are composed of the nefarious inhabitants of Westeros society, the murderers, rapists, the bastards, outcasts and the unwanted. They're sent away to the far north and allowed to live, but only after pledging their allegiance and swearing to protect the realm.
It means they have to spend their entire lives watching the wall, fighting anything that attempts to breach it. It also means they have to remain at Castle Black, the HQ of the Night's Watch, never being allowed to marry or even take a woman to their bed. Unless you're Jon Snow.
This video by Garo Studios pays homage to the motley crew of protectors who have seen the horrors that lie beyond the wall, and have braced themselves for the long winter.
So while we bed down for the long wait until Game of Thrones season seven, check out this tribute and maybe recite the following while watching it. "I am the watcher on the walls. I am the shield that guards the realms of men. I pledge my life and honor to the Night's Watch, for this night and all the nights to come."