How will I know that a customer has subscribed to a product?

I would like to keep track of the number of subscriptions and the products subscribed to. Where can I see this information?

You can see the summary showing the number of subscribers and notifications that had been sent on the Dashboard when you launch the app.

You can also see the details of these subscriptions by going to the Reports section. 

This page will show the products that the customers have subscribed to.