Last week you also heard the term allele used in some of the videos. An allele is an alternative form of a gene. Each parent donates one allele for every gene.
The term homozygous describes two alleles that are the same. Heterozygous describes two alleles that are different. https://youtu.be/H7dvDtcp2Kk
This video also uses the terms genotype and phenotype that you heard in videos last week. Let's take the time to define those as well.
Genotype refers to the genetic makeup of an organism. Phenotype refers to the physical characteristics and organism displays.