When you cross strains, you have a high variance in genetics and the offspring produced will have the ability to possess traits from the mother, father, but usually a combination of both. This first generation cross is known as F1 and planting these seeds is like the lottery. Siblings may look different and at times look better or worse than the parents. It is not until these crosses are crossed for you to see better combinations of traits you desired from the original parents and this second generation is known as F2. Strains are different from crosses and they are usually the result of at least 5 generations of selective breeding which stabilizes desirable traits. Strains are more consistent when it comes to looks and taste.