Explain how organisms are genetically unique..?

This is for a Biology paper that I am writing. The question is: "Explain how organisms are geneticaly unique. In your discussion, define the terms meiosis, mutations, chromosomes, abnormalities and environmental factors. In completing your conclusion, use each of the previously defined terms and use the terms correctly." I will be able to define the terms, but I need to know how organisms are genetically unique and how to use them as examples in my conclusion. Please help!!