F1 Generation. F1 or first filial generation is the
generation of hybrids produced from a cross between the genetically
different individuals called parents. For example, Tt individuals are
produced in F1 generation from a cross between TT and tt
parents.
F2 Generation. F2 second filial generation
is the generation of individuals which arises as a result of
inbreeding of interbreeding amongst individuals of F1
generation.