What are genes and how do they influence human development?

Genes are the term for groups of genetic code, as DNA, that define inherited traits. Genes control all of your physical traits, such as height, eye color, hair color, predisposition for diseases such as Diabetes, and, it is believed, predispositions for behavior as well. They are literally the coding for who you are, both physically, and in some part personality wise. however, your personality is also greatly affected by environment.

In a nutshell: genes are the instructions to your cells for your physical traits and the predisposition to certain personality traits.