What is Albino?
Leopard geckos have three types of pigmentation, contained in three different types of cells: melanophores, which contain black pigment (melanin); xanthophores, which contain red, yellow or orange pigment; and iridophores, which contain crystalline materals that reflect and refract light.
Albinism is usually when animals cannot produce melanin because they lack the essential enzyme tyrosinase. Albinism in leopard geckos is apparently slightly different, because they are not true albinos but rather extreme amelanistics, which roughly means that they produce virtually no melanin, but still have the potential capability to do so (because all strains do in fact have tyrosinase). Since it only affects the melanin pigmentation, albino leos can still show orange, yellow and brown coloring.
Tremper, Rainwater and Bell (Albino)
There are three strains of albinism in leopard geckos, which are each recessive. The "defective" gene occurs at a different allele for each strain. That means that crossing, say, tremper with tremper lines will get you albino offspring, whereas crossing between lines - say, tremper with rainwater - will get you normal offspring.
As for distinguising between the strains, it's not so easy as you might think. Looking at each strain as a whole and comparing it to other strains shows some differences, but since there is a lot of variation in pigmentation and patterning within each strain, looking at a single leopard gecko of unknown lineage may not tell you which strain it comes from. Having said that, there are certain traits you can look for in order to make a good guess - the most distinctive of which seems to be the eyes.
Trempers are the most common type of albino in leos, and also the first discovered. They have pale or silver eyes, often with red veins showing in the eyes. Sometimes the eyes start off pink but turn silver as the gecko matures. Trempers are more likely to have brownish markings on them than the other two strains.
Rainwater albinos (also known as Las Vegas albinos) are smaller than the other two types, and they have darker eyes. They are usually paler in general, with more pink coloring.
Bell albinos are the most recently discovered. Their light pink eyes are their most distinctive feature. They also often have lavender coloring, and small brown spots.
False albinos
There are other morphs which are not genetically albinos, but might be confused with them.
Patternless (leucistic) geckos have no dark pigmentation but normal-colored eyes. As babies they have a unique spotted appearance around the head and shoulders.
Blizzards are similar to patternless geckos; typically greyish but could have a background colour of anything between white and yellow.
Hypomelanistic “Hypos"
have a gene which reduces the distribution of the black markings making them have very small number of black markings on the body, but they still have markings on the head and tail. ("Super-hypos" or "baldies" have no markings on the head either.)
Snows are axanthic (lacking the yellow pigment) which means they have a high contrast black on white pattern.
There are also combinations of the above with the various albino strains, creating morphs such as The blazing blizzard (albino trait and blizzard trait, making them pure white) or patternless albinos.