This is the 7082nd most frequent Russian word.
бесплатно
Free (of charge).
In this sentence, 'бесплатно' is used as an adverb, describing the manner in which the tickets were acquired (without cost).
Мы получили билеты на концерт бесплатно.
We got tickets to the concert for free.
Here, 'бесплатно' functions as an adverb to explain the condition under which the samples are distributed.
Раздают бесплатно пробные образцы духов.
They give away free samples of perfume.
In this example, 'бесплатно' is used adverbially to indicate the absence of cost associated with downloading the application.