What are channels and subchannels?
Channels are groups of users that share a common interest. They are usually used for user segmentation and targeting. You can add subchannels under a channel to further segment your users.
Example: 'Sports' and 'Travel' channels for your news app. Subchannels 'Soccer' and 'Basketball' under the channel 'Sports'.
You can choose to send a notification only to a particular channel/subchannel in the 'Create Push Notification' dialog.