What are Service-profiles and Gateway-profiles for?

What does it start for Service-profiles and Gateway-profiles? Please explain me
Can I create one for each and use on all devices?

Service-profiles - for applications, which You create(ed) in your Chirpstack
Gateway-profiles - for gateways which You add to your Chirpstack

Can I create one Service-profiles and attach to all applications?

For what Add gateway meta-data and Enable network geolocation? Pls explain me

in case when your GW has hw GPS/GLONASS/etc. module or You enter GW coordinates in the GWpacket forwarder config file manualy.