The Leader is usually the person who starts the co-browsing session, and the Followers are the users who join.
The Leader is therefore also the person who has control over the navigation. During co-browsing, control can be switched if you make this possible in your settings, but the leader is always able to take control back.
It’s good to keep in mind that it is the Leader’s browser that is shared with the others, so changes that are made during co-browsing are made to the Leader’s browser. The same goes for cookies, as they will be stored on the Leader’s device only.