Genetics is a branch of science which deals with inherited characteristics shared by generations of organisms. There are many possible ways of using the term.
You could state that your height, weight, hair color, or other physical features are determined by your genetics. You could track the genetics of prize-winning animals in an attempt to identify the best male and female to breed to produce a superior animal. You could explain that the genetics of a species changed as it evolved and changed over millions of years.
Genetics can also be used to describe characteristics of a group. You could discuss the genetics of the football team of your school as being different from the genetics of the chess club.