Google is offering a feature – to both free and paid members – that neither Apple Music nor Spotify can boast of: you can upload 50,000 of your own songs onto the cloud, and then stream them from anywhere. The only requisite for all of this being that you must have a Google account. Apple has something similar in iTunes Match, but you've to pay for it separately, on top of Apple Music.
Of course, if you're willing to pony up the price of half a coffee at Starbucks, you get other advantages too. You can download as much music as you like, and listen offline later. Sure, Apple Music has that too, but it doesn't have a Web-based UI, so you need to use iTunes on your computer.
If you're looking to jump on the bandwagon, and make the most of Google Play Music, here's what you need to know.