This is the 8737th most frequent Russian word.
петербургский
Pertaining to St. Petersburg.
The word 'петербургский' is used as an adjective to describe the noun 'театр' (theater), indicating that the theater is related to or located in St. Petersburg.
Петербургский театр славится своими постановками.
The Petersburg theater is famous for its productions.
Here, 'петербургский' modifies 'путеводитель' (guidebook), specifying that the guidebook is about St. Petersburg and helps learn about it.
Я купил петербургский путеводитель, чтобы лучше узнать город.
I bought a Petersburg guidebook to better get to know the city.
In this case, 'петербургский' describes 'акцент' (accent), indicating that the accent is characteristic of people from St. Petersburg.