What does the following equation represent?

The given equation represents the gene frequency of the total population according to Hardy-Weinberg law. In this equation, suppose a gene has two alleles A and a and p is the frequency of occurrence of the dominant allele A and q is the frequency of occurrence of the recessive allele a in the parental generation. Then according to the equation, p² + 2pq + q² = 1, where p² = frequency of occurrence of individuals with homozygous dominant alleles (AA), 2pq = frequency of occurrence of heterozygous individuals (Aa), q² = frequency of occurrence of individuals with homozygous recessive alleles (aa). The sum total of all allelic frequencies is 1.