Going back to elementary school when we learned how to draw a triangle, you were told make a closed form from three straight lines. Three straight lines was the rule, and anything meeting the rule was marked correct. Of course many differing forms are correct since there are many triangle possibilities.
Plants behave in the same rule based way with even a greater number of differences. The rules are the genetics; the outcome is the phenotype. Simple yet complex.
Genetics provide an architectural blueprint for building a plant, but reality comes into play as the site manager directing all the molecules and chemicals into a finished product.
What kind of soil is used, what nutrients are added, temperature, light type and amount, length of flowering time, drying process, curing and more all impact how the blueprint is interpreted. This is how the same genetics can produce the strain White Widow and the phenotype Jean Guy as a separate strain.
White Widow is a balanced hybrid boosting conversation and creativity with an euphoric and energizing high. The buds give off a pungent, not to be ignored, ammonia-like scent tinged with pine. Compare this to Jean Guy that is strongly Sativa Dominant and known for a sour, citrus scent that is energizing but can send ones thoughts flying too. These two hardly sound like the same genetics, and that is phenotypes for you.