Difference between chat sessions and user session?

What is the difference between chat sessions and user sessions?

A user session represents a bi-directional connection between your client application and ChatKitty while a chat session represents the duration a user is actively engaged and chatting in the context of a channel.

What happens when a user session is open but chat session is not but a message is received in that channel?

In-app notifications are sent in the case that a user is online but doesn’t have an active chat session related to an event.

This article covers this in more detail