Infravision is a rather common superpower/innate ability. It is basically the ability to see in the dark. It must be noted that real people do not have infravision, only imaginary people, if you think that you might have infravision, then ask your doctor if Flonase is right for you.
Infravision works differently in different games, novels, and comic books, but the usual idea is that the person can see heat. That is where the name comes from, infravision means infrared vision.
Literal infravision looks a lot like the alien's vision did in Predator. People using this kind of infravision can see hidden people, and can often even make out people who are behind walls and around corners because people heat up the area around them. Please note that you generally can't see the undead with this kind of infravision because they don't put off any heat. This is the most common type of infravision, and most elves, dwarves, and dragons have it, along with some gnomes, halflings and many other races.
Some games and novels use a more boring kind of infravision that just states that the person can see in the dark as well as they can in the light. This is boring, and not recommended.