Atkins is just one of many low carb diets out there, though it has probably the largest following.
Here are the basics:
Carbs consist of sugar, fiber, and other compounds. Food are the carb rich are breads, fruits, pastas, rice, etc.
Low carb foods are beef, chicken, fish, eggs, cheese, nuts (certain nuts), some vegatables (mostly greens), and lots of others.
Here is what basically happens when you ear carbs. Certains carbs raise your insulin levels (fiber and several others don't), which in effect turn on your bodies signals to store fat. It also burns some of those carbs, but in society today we tend to eat WAY too many carbs. Our bodies aren't made to eat all the grains, flour, sugar that we consume. We are omnivores, but our bodies are made to eat, vegatables, meats, greens, nuts, and some fruits. Over the last thousand years, flour and sugar based foods has been a staple of our diet and our bodies can't process it efficently, so it stores it as fat.
Here is what happens when you limit your carb intake and increase your protein intake. Your insulin level drops (to a still safe level) and your sugar level lowers. This in turn switches your body from storing fat, to burning it. Your body starts releasing ketones and it uses the stored fat on your body as it's primary fuel source. Your secondary source of nourishment is the protein that you are eating from the meats, cheeses, etc.
While you are on the low carb diet, you WILL LOSE WEIGHT! It's guarenteed as long as you stick to the plan. Once you get near your ideal body weight, you can start gradually increasing your carb intake to a reasonable level. When you start gaining weight (fat) you need to back it off. Your body will tell you when you are eating too much carbs.
This is just the basics and I'd encourage you to read Dr. Atkins "New Diet revolution" before starting the diet. If you don't, you'll most likely fail as you'll get frustrated when things aren't working as you think they should. This is most likely because you are eating a food/foods that are high in carb and you don't even know it. The book teaches you what food are high and what foods are low. It also teaches the science behind it, so you understand what your body does with all the food it takes in.
If you have any more questions, see the link in my sig.
Jugs
EDIT: Btw, as for your question
Aren't you incredibly void of any and all energy?
Absolutely not! I have way more energy now that I'm on the diet then I did before. I walk 4 miles a night and ride my bike a few miles every few days. I've lost 60lbs in around 4-5 months. I couldn't be happier!
Why dont you just eat healthy and exercise?
That is what you are doing on the Atkins plan. You can lose weight without exercising, but you'll be in much better shape phsycially if you do some cardio and weight training.