A redline often starts with two parties and then needs a third person. Counsel, a colleague, someone who has to look at one section. Sending them a copy of the file starts a second draft.
You can add another person to a negotiation so they can work on the same draft with you. The invite adds them to that redline request. They join the document that is already in progress, and they are notified by email.
They are on the same turn structure as the party they joined. The contract stays one draft, with another person able to work it, instead of a forwarded file that has to be merged back later.
