It's build on Twitter Bootstrap 3 for the UI kit and has redesigned icons, updated modal layouts, and consistency in button, form, and link styles. It really has made CPanel go from looking like an ugly 1997 web interface to an elegant software application.
If you are a reseller or a VPS customer you can enable the theme in from WHM by doing the following steps:
* Log into WHM
* Click Modify an Account in the sidebar.
* Select an account and click Modify.
* Select Paper Lantern from the cPanel Theme menu and click Save.
* Log out and then log back into WHM to see your new theme!
Several of the feature names used in x3 have been changed in Paper Lantern. Some features have also been moved to different sections of the Paper Lantern interface.
Some names within the interface have changed and some have been moved to different sections in the Paper Lantern UI, though not so much that I think it'd take anyone very long to figure out where to go. That said if you activate it and kind figure something out here's a handy cheat sheet: https://documentation.cpanel.net/display/PLD/Paper+Lantern+Cheat+Sheet