NBC NEWS — With traditional digital music purchases, you buy a song and it's downloaded to your device, and you can only listen to what you've purchased.
But with streaming music, you're not limited to a download; you can listen to songs on demand, using your internet connection.
You pay monthly, but can listen to millions of songs. And what's more, there are some free options available.
"You don't have to prepare. It's right there on the spot and it's a humongous library of music," said tech expert Rosa Golijan.
A handful of these services are quickly growing in popularity. Each with their own distinct features, says MSNBC.com tech writer Rosa Golijan, such as Spotify.
"Spotify has this collaborative playlist feature and you can create a playlist, you can share it with your friends, and they can add songs, delete songs. And one of the best things about it is that everything syncs instantly," said Golijan.
Have tons of facebook friends? Mog may be right for you. You get credit for promoting the service. The more you promote, the more you fill up credits in what's called your gas tank, keeping your listening free.
"You can listen to them and then you can complete some tasks to listen to more songs. So you're working for your music...by actually using it you're earning more, you're refilling your gas tank," said Golijan.
Interested in discovering and sharing music through friends? Check out Rdio.
"You can really just see your friends' playlists. I mean who do you really want to discover music from? Back in the days of mixed tapes and mix CD’s, you got music from your friends. That's a little jump back to that and a lot of people love it," said Golijan.
If you'd rather have a DJ for your music discovery, there's Rhapsody.
"There are radio stations that play artists based on more suited to moods or specific rock, pop, whatever and they are some of the best handpicked songs out there, so that's Rhapsody's big strength," said Golijan.
But there is a word of caution if you're streaming to your smartphone: Keep an eye on data usage.
"If you're going to be streaming, whether it's video and audio you definitely want to be on wi-fi because it can eat up your data very fast,” said retail sales consultant Shondale Lewis.
As for choosing a service, it's simple trial and error. Decide how you want to listen, discover, and share music. Each cost, at the most, about $10 a month or less, and all have either free versions or free trials.