Genetics is the area of biological study concerned with heredity and with the variations between organisms that result from it. In other words it is the field of science that looks at how traits are passed down from one generation to another, through genes. Genetic traits are things we can see with our eyes that are the result of having certain genes, for example hair color or eye color. Each person has thousands upon thousands of genes that contribute to our appearance as well as who we are.
Genetics plays a large role in determining the appearance and behavior of an organism, but environmental factors determine the ultimate outcome. For example, while genes play a role in determining how tall a person will be, it also depends on the food and health that a person experiences during childhood