Infravision is a spell which allows characters to have limited vision in the dark.
cast infravision cast infravision <character>
This spell enables the character to detect the heat signatures of other players and creatures in the same room with them when there is no other light source present. 'Infravision' will also allow you to find items in corpses, containers, etc. but will not allow you to view the actual contents.
You must have a light source to actually see items, room descriptions, the contents of corpses or containers, room exits, and the like inside a darkened area.
Infravision is not the same as "night vision".
Races who are imbued with 'infrared' have this ability naturally.