Question: how are a heterozygous and a homozygous individual different?
Answer: Homozygous carries similar alleles of a trait. E.g. RR, rr, while heterozygous carriers dissimilar allele e.g. Rr. A homozygous individual can carry either dominant or recessive allele, but not both at a time; a Heterozygous individual has both, i.e. one dominant and one recessive allele.