in simple language, it is a benefit in the policy where a member can sue another member. Without thaat benefit/extension, a member could not sue another member.
in the event of a claim covered by the policy, the insurance company picks up the bill. You might have an excess though - have a look at the policy wording or contact your broker.
just because you would not have the policy benefit of member to member, would not prevent members suing each other. The only difference being that the losing member would have to pay the winning member himself!