Darkvision

Within a specified range, a creature with darkvision can see in darkness as if the darkness were dim light, so areas of darkness are only lightly obscured as far as that creature is concerned. However, the creature can’t discern color in darkness, only shades of gray. When a creature with Darkvision is in dim light, it will see as though in bright light, again up to the specified range.

i.e. An Elf standing in a dimly lit forest will see it as brightly lit up to 60 feet, and then dimly lit beyond that point. When night falls and the Elf is in darkness, the Elf can see 60 feet as dimly lit, and then darkness beyond that point.

List of Races with Darkvision

 * Dwarves - 60 ft
 * Elves - 60 ft
 * Drow - 120 ft
 * Gnomes - 60 ft
 * Half-Elves - 60 ft
 * Half-Orcs - 60 ft
 * Tieflings - 60 ft

NOTE: Any race that has taken the Warlock perk "Devil Sight" has Darkvision up to 120 feet and can see through even magical darkness.