The word chotlh means "stare at" or "gaze at" or "observe." You'd also use it (often without an object) to mean staring off into space, staring at nothing in particular, zoning out. So it's used when you're looking at something intently, with a lot of focus, but also when you're not particularly focused. It can also be used for "ogle." Context clarifies which sort of connotation is intended.