Message catchers
For each log, you can configure which messages should be captured in it. For example, you may want to capture your current group messages in the raid log as well.
General chats selection
The dropdown that lets you select which general chat to read. There is also one for misc. (achievements, item loot, system messages) and custom channels (the ones you manually join).
Copy window: BBCode
You can also output the logs in a BBCode format, so you can paste that directly on forums. No need to manually type chat or item colors anymore!
Main window
That's where you read the logs and select (on the top right) which chat to show.