Media Mail is used for any type of movie, book, documents, and Music. These are the only things you can send at this rate. Yes you can go to the Post Office. It is particularly good for multiple items of this type. I ship daily at least 20 items per day, so I am well versed in this. I can tell you right now, if you use this for anything I listed that is 9oz or more, you will save vastly on shipping. For instance these two together would cost around $3.50 to send, and an extra .80 for delivery confirmation if you choose to track your package. I print my postage at home, through Paypal Multiorder shipping and just use a small kitchen scale to weigh and it works out great. Otherwise, if you are going to the P.O. anywhay, they can weigh it for you, and just specify Media Mail, it is that easy and will save you a few bucks in shipping, as well as your buyers.