This is the 13178th most frequent Polish word.
ogłoszeniowym
"Ogłoszeniowym" means "advertising" or "relating to announcements."
Here, 'ogłoszeniowej' is used as an adjective to describe the type of board where announcements are made.
Wziąłem długopis i napisałem coś na tablicy ogłoszeniowej.
I took a pen and wrote something on the announcement board.
In this sentence, 'ogłoszeniowemu' is used as an adjective to specify the type of portal dedicated to posting advertisements or announcements.
Znaleźliśmy nowe mieszkanie dzięki portalowi ogłoszeniowemu.
We found a new apartment thanks to the classifieds portal.
Here, 'ogłoszeniową' describes the newspaper as being focused on advertisements and announcements.