Offline Mode is a feature in a streaming music service that allows you to listen to songs without the need to be connected to the Internet. This technique relies on the utilization of local storage space to cache the necessary audio data. Depending on the type of music service you subscribe to, you can have offline access to your favorite songs, radio stations, and playlists. The software used by the music service for caching audio is also important. This can be restricted to just a desktop app that downloads the necessary audio data to your computer's storage. Most streaming music services that offer this offline option usually develop apps for various mobile operating systems that enable the caching of music on portable devices too.
The advantage of using a music service's offline mode is primarily to play your cloud-based music collection when you don't have an Internet connection.
Many music services that offer an offline caching facility for music tracks also allow you to sync your cloud-based playlists to your portable device too. This creates a seamless way of enjoying your music library and keeping your playlists in sync without you needing to be constantly connected to the music service.
If you are paying a subscription for a streaming music service that has an offline mode then the files you cache will come with DRM copy protection. This is to ensure that there is sufficient copyright control over the songs you download and that the music service can maintain its licensing agreements with the various record companies involved. There is an exception to this rule; if you are using a cloud storage service that enables you to upload your own music files in order to either stream or download to other devices, then DRM copy protection won't obviously be in operation. This is also true if purchasing songs in a format that is free DRM restrictions.