This is the 13292nd most frequent Russian word.
мотоклуба
A "motorcycle club."
In this sentence, 'мотоклубу' is used in the dative case, as the verb 'присоединиться' (to join) requires its complement in the dative case.
Я с друзьями присоединился к мотоклубу.
I joined a motorcycle club with friends.
Here, 'мотоклуба' is used in the genitive case to signify possession or relation, indicating 'our' relates to 'мотоциклуб'.
История нашего мотоклуба началась десять лет назад.
The history of our motorcycle club started ten years ago.
In this sentence, 'мотоклуба' is in the genitive case, used to specify the meeting belongs to or is organized by the motorcycle club.