According to Pandora's website:

• Free Pandora is our ad-supported radio service. As a free listener, you can create stations based off of your favorite artists, songs, and genres. We'll take care of curating the music for you, give us feedback on what you like and don't like. Rate music by giving it a Thumbs Up (meaning you like it and want more music like that on your station) or Thumbs Down (meaning you don't like it, or don't want music like that on this particular station). When you give a song a Thumbs Down, that song will not play again on that station again. 

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• Pandora Plus is our first ad-free subscription service. As a Pandora Plus subscriber, you also get the ability to replay tracks, listen to 4 radio stations offline, and you benefit from higher quality audio and a longer timeout period. Pandora Plus is $4.99/month or $54.89/year.

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• Pandora Premium includes all the benefits of Pandora Plus, but also offers the ability to search and play songs on-demand. With Pandora Premium you can create fully customizable playlists, access as much of your music collection offline as your mobile device will allow, and you'll have higher quality audio and longer timeouts than Pandora Plus subscribers. Pandora Premium is $9.99/month or $109.89/year (when purchased directly from Pandora). To find out which devices support Pandora Premium features, see Minimum Specifications & Supported Devices. 

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• Pandora Premium Family offers all of the features of Pandora Premium to up to six unique Pandora accounts, for one low monthly or annual fee. Premium Family is $14.99 USD monthly or $164.89 annually. Taxes may also apply depending on local tax laws in your area.

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Source: https://help.pandora.com/s/article/000001089?language=en_US