What do you call someone who knows all the gossip and stories about people in his neighborhood or surroundings, someone who’s always informed. It doesn't have to be expressed in a word. Could be a sentence (e.g. she knows the ins and outs), but I’m looking for a better way to express it.
You could descirbe them as being in the know. While this often refers to someone knowing confidential information, it can also extend to someone who is just generally well informed.
If you are in the know about something, especially something that is not known about or understood by many people, you have information about it.
I would just call them a gossip
1.2 derogatory count noun: A person who likes talking about other people's private lives.
This is for people whose information comes from a 3rd party, not directly from source.
You don't have to repeat information to be a gossip though, just receive it.
(one's) finger on the pulse TFD
A keen awareness of current trends and happenings.
Sara really has her finger on the pulse of the neighborhood, so I would ask her.
She's very plugged in to what happens with the neighborhood.
Plugged in - closely connected; in touch with what is going on; informed; involved
A rather fancy word for an inquisitive and gossipy person is quidnunc.
a person who is eager to know the latest news and gossip; a gossip or busybody.
Note that this is a noun. It's also rather uncommon in modern usage.
In New York City, the Yiddish loanword yenta is often used:
- A woman who meddles in the business of others; a busybody; a female gossipmonger.
I don’t know how well known this is outside of New York; the English-language meaning of it doesn’t really match the Yiddish meaning of the word (which is more like “gentlewoman,” I believe), and comes from Jewish–American theater (first in a 1920 Broadway play Yenta Telebenta, most famously in the 1964 Fiddler on the Roof, where the busybody matchmaker is named Yenta).
The original word is feminine, and so is the stereotypical yenta, but I have absolutely heard the word applied to men, too.