What goes on an envelope?

Most envelopes have all of this kind of stuff. Here's one the President sent to the folks at WGBH who make this web site. This is who sent the letter. It's their address. If the letter can not be delivered, the Post Office can send it back.

This is who gets the letter. This address includes a city, state and zip code. That way the Post Office knows where to take the letter. The stamp. That's how we pay for letters. It costs 33 cents to get a letter to anywhere in the country. It costs a few cents more to get one to anywhere in the world. I think that's a bargain, don't you?