Keto is short for ketogenic, and is a state that the body may reach once it starts to burn fat instead of carbohydrates. Ketosis is reached generally by reducing the body's daily carb intake to about 20 grams a day. 

The body slowly adapts to this diet change, which is generally high in fat and medium in protein, and starts processing ketones as energy. Common benefits from a Keto Diet is fat loss, increased energy, the feeling of being fuller for longer, better moods and clearer thoughts, and greater endurance.