This is the 1073rd most frequent German word.
beliebte
"Beliebte" means "popular" or "beloved."
Here, 'beliebte' is used as an adjective modifying 'Stadt' (city) to indicate that Berlin is favored or well-liked by tourists.
Berlin ist eine beliebte Stadt für Touristen.
Berlin is a popular city for tourists.
In this sentence, 'beliebte' describes 'Band' (band) to show that the band is well-liked or has a good reputation among the audience.
Die beliebte Band wird dieses Wochenende live spielen.
The popular band will perform live this weekend.
In this usage, 'beliebtesten' is the superlative form of 'beliebte', modifying 'Sprache' (language) to express that it is highly favored globally.