Just google intermittent fasting.
You will have plenty of sources of information to answer all your questions.
There are all kinds of theories as to how it works.
I personally didn't really care to know the details of what was going on 'behind the scenes', I just tried it for myself and was pleased with the results.
I am able to eat a lot of food in 1-3 meals, so it was pretty easy for me to work all day, then train, then eat 1-3 large meals over the course of a few hours before bed.
A lot of guys that haven't done it claim it isn't possible for bigger guys or guys that need a lot of calories to maintain weight or grow. I think it comes down to what the individual is capable of and what food choices you make. I had no problems getting 4k cals down the hatch during IF when I was trying to see if it was possible to gain mass while doing it. I was on cycle at the time, but I did end up growing. It was a nice recomp and I still do variations of fasting pretty frequently. I have always been into fasted morning cardio, and I just ended up staying in a fasted state until I train before lunch. I then eat when hungry for the rest of the day, which is usually about 4 meals. So even though I am fasting from 6am to noon or 1, I am still eating 5 meals a day and hitting the total cals needed to gain weight.