Here's a breakdown:

* Genes: Segments of DNA that provide instructions for building and maintaining an organism. They act like a blueprint, determining things like eye color, hair color, height, and many other characteristics.

* DNA (Deoxyribonucleic acid): The molecule that carries genetic information. It's structured like a twisted ladder, with each rung made up of chemical bases called adenine (A), thymine (T), guanine (G), and cytosine (C).

* Alleles: Different versions of the same gene. For example, one allele might code for brown eyes, while another codes for blue eyes.

How it works:

1. Inheritance: You inherit one copy of each gene from your mother and one from your father. These copies might be the same allele or different alleles.

2. Expression: The combination of alleles you inherit determines how a trait is expressed. Some traits are determined by a single gene, while others are influenced by many genes interacting with each other and the environment.

In summary, genes are the fundamental units of heredity, carrying the instructions that shape an organism's traits.