There are several different types of genes in Mendelian Genetics. The ones we use commonly in reptiles are Recessive, Dominant and Incomplete Dominant. Incomplete Dominant is more often then not mistakenly named Co-Dom. In fact Co-Dominant is two or more genes working together for an alternate outcome. The closest thing I can think of to this in Leopard Geckos since there are no known Co-Dom genetics in reptiles, is that of the Super Mack Snow and Eclipse genes causing the gecko to have an amount of pied. 

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First thing to note Recessive, Incomplete Dominant and Dominant all pretty much work the same. Each gene is in each gecko to begin with. Using albino as an example (any of them), An albino, or properly named a-melanistic is an animal lacking melon, or black pigment. The normal state of this gene could be said to have a working melon production to the cells. If one of these genes is not working, defective, turned off, or however you want to look at it, the melon still gets to the cell. The reason for this is that in a recessive gene, Normal is dominant, or in other words, it takes both copies of a mutant gene, one from each parent to cause the genetic defect to occur. This does not mean the animal does not have the gene, just because it looks normal. What is called a het, is actually heterozygous, meaning containing one copy. The visual albino is actually homozygous, or containing two copies. 

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In the case of the Incomplete Dominant Mack Snow/Super Mack Snow. The heterozygous form is the Mack Snow itself. The Homozygous is the Super. So, the heterozygous is not normal looking, but it is not completely dominant. It's part way there. Just to throw a wrench in this gene too, a "Snow" is actually Axanthic, or missing the yellows. Hyper xanthic is increased yellows, also known as blonde. Snows are usually a combination of both Axanthic and Albino in most reptiles...Funny thing is, that's actually closer to what albino really is. Basically, the reptile world is a mess with it's naming of genetics. 

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Dominant is simply that. A copy from either parent and you've got it. Now it is said that it has been proven that certain dominant genes when the animal contains two copies, that they do in fact produce 100% of their offspring containing the visual gene. The problem is, there is in fact no way to tell if you do have two copies and they look alike. 

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So, to sum it all up, If you breed a single copy animal to a single copy animal (het to het), you have a 50/50 chance of the mutant gene passing to the offspring from each parent. If these are two Mack Snows for example, for every 4 babies on average, one baby will not get the gene at all, two will be Mack Snows and one will be a Super. In a recessive gene, the only difference is that you can see the one in four albino baby, but the other three look alike. The law of averages, says that two of them carry the gene and one doesn't. Since you don't know which without a dna test that doesn't exist yet, you can only say they are possible hets or 66% possible hets to be more precise as it's two of the three babies that are not albino. 

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If one parent is homozygous, or carries both genes, for example the Super Mack Snow or the Albino (Visual not het), then you know every baby must get the gene from that parent and therefore there are no possible hets, all babies will be at least het.

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So:

Super Mack Snow or Albino to normal, all babies are het, the Macks are Macks, the Albinos are het albinos.

Super Mack Snow to Mack Snow, or Albino to het Albino, half are Supers or Albinos and half are Macks or hets.

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As you can see, they work the same, just the recessives are not visual hets and the Dominants/Incomplete Dominants are visual hets.

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And finally, it's not common to say het unless it is a recessive as you would be saying het Super Mack Snow, instead of saying Mack Snow.

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I will try and make this a little easier to follow in the future as I'll probably rewrite it a dozen times, but in the mean time, I hope it makes some sense.

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