During your live stream, your Streamer can gift you diamonds. You can also gift diamonds yourself to show your appreciation to other Streamers. To see how many diamonds you have collected so far, click the profile icon in the top-left corner of the App. You can now see the number of diamonds you have received under your Credits.
Here, you now have the option to redeem your diamonds as a cash or Credit reward. A cash reward means that you can have your collected diamonds paid out as money. If you choose the Credit reward, you can convert your diamonds into Credits and then use them to give gifts to others in their streams.