Het is short for "heterozygous" which means that the trait is carried, but not shown. Think back to biology class with the Punnet squares. LOL.
A snake that's AA (or normal) is crossed with a cc (caramel albino, in this case). That would be AA x cc
Because the normal gene is dominant, it's going to wind up being the one to show in the babies, giving you 100% Ac (or normals het caramel albino).
The crossing of two hets (or Ac x Ac) is going to give you 25% normals, 50% hets, and 25% caramel albinos (if I did my math correctly).
Does that make sense?