Where: A midsized apartment in the center of St. Petersburg.
What: An announcement about a charity concert by a famous opera singer.
Notices about cultural events are commonly seen on the announcement board at work, but sometimes they appear in communal apartments.
Judging from the form of address, the announcement could be meant not only for people in the apartment, but for everyone in the building. However, announcements are never hung in the entrance to the building. This notice was in the apartment entryway by the telephone.
Two details are worthy of notice. First, the invitation is in first person singular ("I invite you"), though there is no signature. Second, though many people are being addressed, the plural "you" is capitalized making it look like the polite form of address to a singe individual. The writer is trying to show that she is highly cultured: she goes to recitals by opera singers, she tries to keep her neighbors informed, she uses a particularly polite form of address. The reader can sense a dissonance, though, because the mistakes she makes are common among people who are not well educated.
The location is given as the "auditorium of the Polytechnic Institute" which is not a lot of information for anyone who doesn't know how to get there from the metro stop of the same name. A person hanging such an announcement on the day of the concert cannot seriously imagine that anyone would respond to the invitation. Thus, the author's motivation is not entirely clear.