(is that even healthy? anyone tried?)

A keto diet means eating very few carbohydrates, so your body starts using more fat for energy.

Carbohydrates are foods like:

bread, rice, pasta, potatoes, cereal, sugar, sweets, juice, regular soda, many fruits

On keto, people usually eat more:

meat, fish, eggs, cheese, oils, nuts, avocado, low-carb vegetables.