Keto is a way of eating where you keep your net carb count under 25 carbs per day. Net carbs are your carbs minus fiber and sugar alcohol, so if you had a food that had 15 carbs but 5 grams of fiber and 5 grams of sugar alcohols, your net carbs are at 5 (15-5-5=5). This way of eating is generally to help people lose weight but can also be used as a diabetic way of eating or can be used for anyone who is trying to watch their sugar intake. I've found that by starting this diet, you essientially cut sugar out of your diet, and you go into a state called ketosis. In theory, ketosis is supposed to make you feel more energized and all around less sluggish than when you're eating a regular carb diet.
Keto is probably one of the most challenging ways of eating I've ever encountered. By cutting out bread, pasta and rice, I've quickly found that I plan my meals further in advance, because I can't just make a quick sandwich and call it a day. I use an app called My Fitness Pal to help me keep track of my net carbs and my calories, as you also have to eat at a calorie deficit to lose weight. It helps me stay on track and holds me accountable for how much food I'm eating per day. It even tells you when a food is high in certain nutrients or saturated fats so that you can know whether or not you want to eat that thing again based on if you go over your limits or not.
I will admit that I still eat fast food on keto, but it's mostly cheeseburgers wrapped in lettuce or just without a bun because that's a quick and easy meal for when I don't have anything planned. For dinners I try to keep my meals cheap but with a lot of vegetables, because vegetables are an essiential part of keto. Some of my favorite meals include cabbage sauteed with sausage, jalepeno popper stuffed chicken breast, spaghetti squash with italian sausage and marinara, mushroom cap pizzas, and of course, bunless burgers. So far, keto hasn't been super convenient, especially when I'm on campus for long periods of time and don't really have access to a microwave, but I've lost 50 pounds thus far and hope to lose even more. Keto has completley changed how I decide what goes into my body and has helped me to eat so much healthier than I did before. Even if I have a cheat day now, it's still not as bad as I used to eat on a regular basis. If you're unsure about it I'd definitely recommend trying it and seeing how you like it.