These beautiful little oddities are unusual for many reasons. One is the obvious from the name; they are very transparent (not apparent from the photo, but look more clear in real life, see links below for more pics).
It is their musculature that is transparent, so you can see the thin bones of their skeleton (their gut and major organs are all compressed to the front end of the animal, and you can't see through that). They are also unusual because they are a non-bottom-feeding catfish; they swim in the mid-to-upper range in small schools of 3-4 (they love the company of their own species). If kept alone, they will not do as well and languish in the corner most of the time. They feed on a variety of meaty foods and love bloodworms or freeze-dried plankton.
They don't have the best eyesight, and will usually only know to catch food when it is sensed by their two long "whiskers", which are sensitive to taste. I've found them to be moderately hardy, and very active fish, swimming back and forth across the full length of the tank, not as shy as many bottom-feeding catfish. They do need open swimming room but have few other special requirements. Glass cats are compatible with most fish and are very peaceful.