What is a GWAS?
Genome-wide association studies (GWAS) identify which variants might increase your chances of having a trait. We use these for complex traits, which are the result of a lot of genes and the environment.
For example, a certain variant might be more common in people with diabetes than in people without it. We would then say that this variant is associated with diabetes.
Usually, GWAS studies have to include thousands of people to discover these connections.