These lectures investigate how bargaining occurs between two rational actors. We begin with a take-it-or-leave-it offer of a discretely divisible good before expanding to multiple offers and continuous bargaining divisions. (The lecture assumes that you are familiar with extensive form games, so you should watch those lectures from the main series first you have not already.)
Ultimately, we discover that there are three simple forms of bargaining power: the ability to make offers, a player's evaluation (or need) of the good, and outside options.