Punnett squares are a tool used for Genetics. Punnett squares are used to predict what your child may look like or different muscles that are not necessarily there. For example, a child with dark hair could have a mother with blonde hair and a father with dark hair. Dark hair is the dominant phenotype other than light or blonde hair.
Punnett squares are easily functional for about anyone to use. In the punnett square below, the dominant "R" falls down into the boxes below it. The recessive "r" goes to the right into the squares beside it. It's very simple to use if you know how to.