Infravision is the ability to see better in the dark, though not as well as Ultravision. Dwarf, Gnome, Half Elf, Halfling, High Elf, Iksar, Ogre, Troll, Vah Shir, and Wood Elves have infravision.
Certain spells some classes get grant infravision. Like the necromancer spell Deadeye. Some items like Crown of King Tranix grant infravision.