What does Taplytics use to distinguish a session? Is there a specific session_id, event_id, network_id, device_id, ip_address or something else that you use?

Taplytics automatically tracks sessions for you. The Taplytics SDK keeps track of the last activity timestamp in your app (app activity is considered a view change, button click, or Taplytics event logged), and when your app returns from the background, if the time since last activity is greater than 10 minutes, we create a new session for you. If you would like the session background time to be something other than 10 minutes, you can set it as a start option.

To do this, please see the SDK docs below: 

Android Docs

iOS Docs