How does computer charger work?

I'm not 100% sure, I came on this post seeking an answer to the same question... But, I do have a general idea of how it works. Basically AC current flows from the wall socket through a cord until it gets to the weird box that is in all computer chargers. This box I assume to be a rectifier. This rectifies, or converts AC to DC thus allowing the current to flow the rest of the length of the cord and charge your battery. Trivial fact: A mac book charger has a single wire coming from rectifier to computer. How is this possible? Doesn't DC operate on two poles? Correct, it does. The charger has an inner wire and an outer wire which are insulated from each other. Hope I helped some.