What is the signing order of an envelope?

Recipients can be requested to sign in two ways:

Sequential: recipients will sign in order.
The first recipient will get an envelope with document(s). The documents he/she signs will then be sent forward to the next recipient, and so on.
Parallel: every recipient will be requested to sign at the same time.
All recipients can sign without waiting for the others.

Once the last recipient signs everyone involved (all the recipients plus the person who created the envelope) will get a copy of the signed document.