This is the 18071st most frequent Russian word.
футбольных
"Футбольных" means "football" or "soccer-related" (adjective, plural or possessive form).
Adjective modifying the noun 'чемпионатов' (championships) to specify their relation to football.
Студенты изучают историю футбольных чемпионатов.
Students study the history of football championships.
Adjective modifying the noun 'команд' (teams) to specify those related to football.
Мы купили билеты на игру лучших футбольных команд.
We bought tickets for the game of the best football teams.
Adjective modifying the noun 'событий' (events) to specify those associated with football.