Epistasis and functional genomics are two different ways of understanding how genes work together in living things. Genes are the instructions in our cells that tell them what to do. Genes work together to make up our body and keep it working properly.
Epistasis is a way of looking at how different genes interact with each other to create a certain trait. For example, when an organism has two different versions of the same gene, these two versions of the gene can either work together to create a certain trait or they can work against each other and cancel out each other's effects.
Functional genomics is a way of looking at how the genes in our cells work together to create cells and tissues in the body. It looks at how our genes interact with each other, the environment around us, and the functions that our genes perform to keep us healthy. Functional genomics looks at the full picture of how our genes work together to make us who we are.