IGMP Proxy & Source Networks questions

I'm not a networking guy, and have questions what those settings do.

I would think the IGMP Proxy would be a good thing to have turned on, but it defaults to off. When would I need that?

My only Source Network is the main LAN subnet. My incoming VPN connections work fine, but they're not listed there. I'm not going to mess with it, but wonder under which cases I should.

TIA,

David