Homing Pigeons

I was walking back from picking up my lunch today when a whole bunch of rats with wings fluttered and landed in my path. Like everyone else around I looked around to see if any were flying above me because I did not want to get shit on or touched by these gross animals. Amway's I walked past the pigeons and started thinking about how these birds can be used to send messages. I wondered how do you train them to fly somewhere and fly back? I picture a pigeon with a string tied to its legs and a man holding the piece of string leading it wherever you want it to go. Like what you did with a June bug when you were a kid!!! Maybe that was just my weird family, I don't know. That is the only way I can think of training the thing to go to places. I cant get it out of my head so I had to look it up. I came up with sites but nothing really explaining what you must do. Also I don't want to spend money on getting this question answered so I started getting discouraged when I kept getting sent to sites to buy a book on training them. Why wont anyone just tell me. I guess I am left to imagine that yes I am right people tie strings to pigeons and walk them around as they fly to train them to come back.