This is the standard sheet that the
United States Postal Service uses as their complete rate sheet for
domestic mail. If it can be acquired (by the consumer) from the postal service or is a service to be had (again, by the consumer), and has something to do with sending mail, you will find its cost in this notice.
So as such, this sheet won't contain many things. This is not a sheet that contains other data (such as the cost of a postal drop box), or the cost of phone cards, or those little commemorative pins you can buy with a nice image of the Dr. Seuss or Henry Mancini stamps.
On the other hand, it can be a little confusing. Many of the services such as priority mail now use zone pricing, requiring you to reference another sheet to determine which zone you are mailing to.
This information is free, and is updated when any rates change. It can be retrieved from your local post office or downloaded from http://www.usps.com in the form of a PDF.