Few use cases:
1) (from customer) Click on an IP address in a Mattermost channel: this address opens the right-hand side panel with more information pulled from an internal database like the OS, browser, etc. Useful for troubleshooting.
2) Clicking on a Google map link or image preview opens the right-hand side panel with more information on the location
3) (from community) Displays a list of GIFs a user can choose from after invoking a giphy slash command