To negotiate means to communicate or confer with another in order to arrive at a settlement. It also means to meet with another to arrive at some sort of agreement or compromise.
Negotiation refers to the action or process of negotiating or of being negotiated.
In short, negotiation is give and take, agree or disagree, yes, no, maybe, and figuring out what you really want. Negotiation can take place before, during or after any sexual activity takes place. Your partner brings it up but you must decide that you want to and that it can be safe. If no, how to keep your relationship open and deal comfortably with different levels of intimacy. You are at a party and a woman you have been interested in asks if you want to spend the night in her room.