Messages In-Out tab shows the graph of all messages which occurred on the system.
Top Messages In tab shows only the most popular keywords among the messages received from the users.
Top Messages Out tab shows only the most popular keywords among the messages sent to the users.
You are able to see the user list of the related conversations when you pick the specific point on the graph.
Also, you may select the message type from the blue button at the right top corner. The options are text, video, audio, image, file, and postback.