When you eat less than 50 grams of carbs a day, your body eventually runs out of fuel (blood sugar) it can use quickly. This typically takes 3 to 4 days. Then you’ll start to break down protein and fat for energy, which can make you lose weight. This is called ketosis. It's important to note that the ketogenic diet is a short term diet that's focussed on weight loss rather than the pursuit of health benefits. 
When something is popular, it’s pretty much a guarantee that people are going to come up with new or easier ways of doing it. Enter the lazy keto and dirty keto diets. With lazy keto, people try to limit their carb intake to 20 to 50 grams a day but don’t really track it; with dirty keto, people generally follow the same macronutrient breakdown as "regular" keto, but it doesn't matter where those macronutrients come from.
It can take many weeks for someone to notice differences. If you’re weight training and doing the diet you may not notice weight loss immediately because you are growing muscle and muscle is heavier than fat. Elsewise, for me I went really strict starting out. I did under 30 carbs a day for the first week and measured my ketone levels with the piss sticks you can buy at cvs and was entering ketosis after 3 days. I went up to 40 carbs a day for the next 3 months and lost 60lbs of fat. I was 287 lbs and weighed in at 227 when I finished. Mind you I exercised daily doing heavy weight training and intermediate cardio. The diet does work though. I did put on lean muscle while getting down to a healthy weight for my height. It helped with my panic disorder as well as giving me a lot of energy.
Tracking protein is important for anyone who has adopted a ketogenic diet. Depending on activity level and other metabolic factors, some individuals may be able to tolerate more protein. As mentioned above, at a certain level protein can be glucogenic; so tailor it to your needs. However, we would say to lean towards more, not less, especially for older individuals trying to preserve muscle mass.
Achieving optimal ketosis hinges on finding the right balance of macronutrients (or “macros” in keto-speak); these are the elements in your diet that account for the majority of your calories, a.k.a. energy—namely, fat, protein, and carbohydrates. By the way, it’s often “net grams” of carbohydrates that are counted toward your daily intake; “net” deducts the amount of fiber in a food from its carbohydrate total.