via:
William Blankenship
A central point in the government’s mass surveillance program is distinguishing between “content” and “metadata”. Content is the actual communication, like Smith’s voice in a phone call. Metadata is information about a communication; the phone number Smith dialed. For example, when we send a letter in the mail, we could call everything inside the envelope “content”; the mailing address, return address, weight, date sent, date received, postage paid, who paid the postage, etc. could be called “metadata”.