Being subscribed to a board means you are interested in always receiving updates regarding the specific board.
Here is how to subscribe to any board from your mobile phone:
Go to your board and click on the three dots located on the upper right of the screen.
Once done, select subscribe and you are done :)
If you have any further questions about how to subscribe to a board on Android pease don't hesitate to contact our customer success team just right here. We are here for you24/7 !