A Customer Session describes the activity of your end user within your application, such a single order or a billing cycle. Similar to a customer profile, the unique identifier of your customer session is controlled completely by your integration. Information about the customer session is pushed by application plugins to the Talon.One API. 

For example: The process of your customer (end user) purchasing an item in your application, shop or system

Read the technical explanation of Customer Sessions in our Developer Center.