[meiji]

Essentially, you can "sell" rights to negotiate with you exclusively. It's often used so that the seller can focus on a single party but gets a reasonable payoff if the sale doesn't go ahead for any reason. The other party therefore has to commit resource and won't just do it for the sake of doing it. I've usually seen it done when there are, say, 3 or 4 interested parties to narrow it down to 1 in the first instance. On some occasions the party that had exclusivity drops out and it's either a good thing as the other parties are still there or a bad thing as a serious buyer dropping can raise alarm bells.