What does the word "connection" refer to in this context? A bond, I presume?

What does "indicator" mean?

An "indicator" is a thing that indicates the state or level of something. It can be a form of measurement, or a trend or fact that represents a bigger insight. Here, "how people stand is a strong indicator or their mindset" means that one's stance can represent how one thinks or feels about the world. Ex: Rising summer temperatures is a strong indicator that climate change is getting worse. Ex: Colder weather is an indicator that winter is coming.

What does "bank" mean in this context? I assume it has the same meaning as "sector" or "district"?

You are correct! "Bank" in this context indicates a sector or a district of a city. The West Bank is a section in Israel where the city of Jerusalem is located. A bank can also be a bank of a river, which means the edge of the river. Ex: He lives on the northern banks of the city. Ex: We are on the bank of the river.

What's "trick or treat?"

"Trick or treat" is an expression said by children when they dress up in costumes and go to people's houses to ask for candy (treats) on Halloween. "Trick or treaters" is thus the name used for the kids who go trick or treating. Ex: Trick or treat, trick or treat, give me something good to eat! Ex: I used to go trick or treating every Halloween as a kid.

What does the word "connection" refer to in this context? A bond, I presume?

Yes, that's right! A "connection" does refer to a kind of bond between them, like a friendship. Ex: I've made a bit of a connection with my neighbour. She invited me for dinner! Ex: Five minutes after meeting my dog, River, I had formed a connection with her.

What does “narrow something down” mean?

To "narrow something down" means to make a list of choices or options smaller by eliminating them down to a smaller amount. Ex: I still don't know where I'm going to college yet, but I've narrowed it down to three options. Ex: When I don't know the answer to a test question, I start by narrowing it down.