Allele. a particular form of a gene at a given location on a chromosome. Geneticists use the term character for a heritable feature, such as flower color, that varies among individual. Each variant for a character such as purple or white is called a trait. Dihybrid cross. a cross where two different pairs of alleles are involved. Genotype. the total combination of an organism's genes. Homozygous. a genotype where both alleles are the same. Heterozygous. a genotype where the alternate alleles are different. Monohybrid cross. a cross where one pair of alternate alleles is under consideration. Pedigree. A family tree describing the occurrence of heritable characteristics in parents and offspring across as many generations as possible. Take a look at what the symbols in a pedigree chart mean. Phenotype. the combination of observed or measured traits, generally what is readily visible. The symbols P1, F1 and F2 are used to designate first and subsequent generations in crosses. True-breeding individuals are homozygous, alternate alleles are identical, offspring are identical to parents.
"P1" stands for the parents. "F1" stands for the cross between the parent strains. "F2" is a cross of (2) F1's....and so on. F2's Traits vary more than f1's. As a pheno is crossed the hybrid becomes less stable. They grow more vigorous, but the traits become different between two seeds from the same plant.
Backcrossing is one of the parts of stabilizing a strains traits. but there is a lot more to trait isolation and allele purging than I even grasp yet.
Google Mendel's Law.