for three marks you would say Conciliation [something, for example, is not necessarily legally binding] WHEREAS (VERY important use this word) arbitration [contrasting point, e.g. is legally binding]. Depending on your response, for the third mark, add examples for each or elaborate on the differences for about a sentence or so. MAKE SURE YOU SAY WHEREAS, or on the other hand, or however, something that signposts that there is a difference, else you wont get any marks