It's likely that it is the hyperlane that allowed Luke to safely get to the planet where we find him at the end of Force Awakens.
"Hyperlanes were routes through space in which a spaceship could safely travel without colliding with a body in space, or some other phenomenon such as a black hole.1 There were five major routes in the galaxy, with hundreds of secondary routes and thousands of minor ones. Scouting new hyperspace routes was an incredibly dangerous task for an explorer.
In many parts of the galaxy hyperlanes also involved periodic re-entry into realspace. This was so as to manually maneuver the ship towards the next hyper-point." -Wookieepedia
"Hyperspace routes—also called hyperspace lanes—were an established path through hyperspace, which linked major worlds, just as roads linked major cities on populated worlds. Those routes were regarded as safe, allowing starships to travel without colliding with a body in space." -Wookieepedia
Supporting this idea, a CinemaBlend piece (Star Wars: The Force Awakens' Mysterious Map And What It Might Really Mean) speculates that it is a map, started by Darth Vader, to a Jedi Temple which Luke travelled to, to learn more about the Jedi and to defend the temple.
"Whatever was left of the Empire after The Return of the Jedi was dust by this point, so how did they get any of the map? We think it's because they already had it. But for a different reason than "finding" the missing Luke Skywalker. Let's piece this together." -CinemaBlend