Short as I think I can make it. Genes come in pairs. If the snake is normal we say it has 2 normal genes. Sometimes the gene mutates and it will make the snake look different. If the snake has one normal and one mutated gene we call it heterozygous (like pastel or het albino) and if it has 2 mutated genes we say it is homozygous (like super pastel or albino)

Depending on how the snake looks in heterozygous and homozygous compared to normal, we classify the genes differently.

Heterozygous Homozygous
Dominant Visual Difference Same Visual Difference
Co-Dom/Inc-Dom Visual Difference Different Visual Difference
Recessive No Visual Difference Visual Difference