Similarities between heterozygous and homozygous genotypes?

they both have two alleles

they both express the dominant allele (aka the phenotype or physical traits of the allele). They are different in genotype though, which is their genetic make up because homozygous would be two dominant alleles and heterozygous is a combination of dominant and recessive allele. Homozygous recessive and heterozygous are completely different though in genotype and phenotype.