Documents reside inside Envelopes. Basically an envelope consists of 4 parts, the document, the Recipients, the email notification subject/body, and the fields/tags added to the document. Think of this as an electronic envelope just like a paper envelope where you insert a document, address it, perhaps add instructions or a note, and little arrows or sticky notes on where to sign. So when you send an envelope you are always sending a document along with that envelope. Of course you can have multiple documents in the same envelope.