The Keto (or Ketogenic) diet is a low carb (or carbohydrate), moderate protein, high fat diet which puts your body into a nutritional state of ketosis.
How do you get into ketosis?
You have to starve your body of carbs (sugar) for your body to switch over to using fat for fuel instead of glucose.
What are net carbs?
Digestible carbs break down into sugar (or glucose) in your body which will raise blood sugar and affect insulin levels.
While protein is very important for your body, you want to be careful not to eat too much. Too much protein can be hard on your body, make you not feel well, and cause an insulin spike.
If you do eat dairy, I recommend eating grass-fed dairy because it contains nutrients that conventional dairy just doesn't have.