To answer your question , I must say
1. Yes, it's really help. But you have to be very careful using it. Otherwise it will only cause your time and money.
2. It's easy. You just follow the instruction.
3. It will display on your audience that you choose when you create your ads.
Tell you the truth, it's useful, but you need to learn so your ads doesn't cost you.
Hope this information helpful, but if you have any question, please don't hesitate to contact me