How does bitcoin works?

I have read many articles regarding sticks, business, investments but the most thing i am curious about is the bitcoin. I want to invest but I still want to learn on this things because there is a money involved. And of course the future also depends on it. Is there any legit online which concerns to this? And a minimum $1 is allowed for investment, Just to know how this thing goes. I hope I can learn from sites and have more knowledge before joining this.