What is the key difference between the two? I see that both of them delegate the authority to underwrite certain risks on your behalf. Under LineSlip, a follow underwriter allows the lead underwriter to underwrite risks on their behalf, whereas in a binder, an insurer delegates the authority to underwrite certain risks on their behalf to the brokers. Is this the only difference? Also, correct me if i am wrong, but I believe that the underlying contract in a Lineslip should be called a binding agreement.
Not a lot of difference. A binding authority (binder) is a delegation of authority, and a lineslip is an example of a binder that is more commonly associated to a Lloyd's arrangement between underwriters. If you search around, you'll find all sorts of articles online giving you more details (and it's not exactly clear cut), eg https://www.i-law.com/ilaw/doc/view.htm?id=130853
