Audiomack is a completely free platform for content creators to share their music without limitations or restrictions. They focus exclusively on new, independent, and up-and-coming artists. They are not a full-catalog streaming service like Spotify and/or Apple Music, and do not plan to ever become one.
In the same way you use services like Twitter, Facebook and Instagram to promote your music, Audiomack can be used along side Spotify, Soundcloud and other music platforms to share your music.
Audiomack is also completely free to listeners (though they do offer subscriptions if you want to listen ad-free). The service encourages their listeners to use the service as a compliment to other services you use to get your music, rather than the only music app you use.