Dumb question FTM

This might be a really dumb question but I seriously need to ask it. I’ve always wondered and can’t find the answer to it. So I’ve seen women who have breast fed there children. How is it that women can breastfeed for 2 years for there child but others can only do it a couple months. I know milk dries or or you can’t produce enough but how do you get a milk supply to last 2 years. Don’t understand. Please don’t take this wrong for asking from my eyes a good question, like bashing me for asking a simple question. (I know some women can be rude and unhelpful).. I’ve been thinking about how long I wanna breastfeed but not sure if I’m able too.

-TIA 💙💓