There is a social aspect to the Zuora Billing and Zuora Payments modules in that they facilitate communications between two companies (a vendor and a buyer) around the monies owed and paid related to a contract for services.
The Settings > Payments > Setup Profiles, Notifications and Email Templates page provides access to Zuora's Customer Notifications feature, which allows you to automate communications with your customers, using email and callout notifications. Email notifications are sent to your customer, and callout notifications send information to a specified web page or URL (via an HTTP/HTTPS call to an external web service). Both types of notifications provide information regarding events that occur in Zuora Billing and Zuora Payments.
See Notifications and Callouts for information about creating and using these features.