Thanks for writing about this here in the Community.
When music is not played directly using the app, Spotify will add to your music's stream count if, for example, a shared link to any of your songs on Spotify is used to access the songs (e.g. through an Instagram story). This type of streams is what you see under the Other category when looking into your Sources of streams stats on Spotify for Artists.
For more info regarding how Spotify counts streams, take a look here.
Hope you'll find this useful. Cheers!