Allotype is a big, fancy word that scientists use to describe different versions of the same protein in our bodies.
Think of our proteins like a building block toy set: there are lots of different ways to put the blocks together to make different shapes just like there are lots of ways to make proteins. Scientists have found that sometimes people have different versions of the same protein called allotypes that can be slightly different from each other.
To make it easier for scientists to talk about the different versions of a protein, they give them special names like letters and numbers. So, if one person has a protein with a letter "A" and another person has the same protein but with a letter "B," they are called different allotypes of that protein.
It's like if you have two different colors of Lego blocks, you might call them "red blocks" and "blue blocks" so you can tell them apart. Except for scientists, they use special names like "allotypes" and "allele designations" to keep everything nice and organized. Pretty cool, huh?