For a request to progress, it needs to be accepted. After a request has been opened you will be able to review the terms and negotiate.
Following this, if you approve of the terms you can accept the request. After accepting the request your partner will be notified - this is not binding at this stage. Both parties need to accept the exact terms.
To make the deal official, the other party needs to accept the deal. This serves as a double confirmation to ensure that both parties agree on the latest terms. Once a request is accepted, the supplier can provide a release reference.