The Keto diet is the ketogenic diet. The idea is that you get the vast majority of your calories from fats (oils, cheese, nuts, fatty meats, butter) and severely restrict your carbohydrate intake. Macronutrient splits would typically look like 75% fats, 20% protein, 5% carbs. When you have been doing this for long enough your body will adapt and begin to use stored fats on your body as the primary energy source rather than the carbs that you have recently ingested. This process is called ketosis. Once this occurs it is easier to lose weight. Think of it as trying to convince your body that you are starving and that it needs to use the emergency fat stored in your body to survive.
Benefits of the keto diet is that due to the high fat diet, people often remain less hungry while eating less. It can take 1-4 weeks to enter ketosis, and once you are in, having a carb heavy cheat day can knock you out of it for multiple days until you return.
So it is a bit restrictive of a diet, but if you enjoy eggs, avocados, nuts, butter, bacon etc you likely won't have too much trouble with it.