https://www.theverge.com/2017/10/23/16523832/microsoft-xbox-360-games-enhanced-xbox-one-x

Microsoft is extending its Xbox One X Enhanced program to existing Xbox 360 games. IGN reports that four Xbox 360 games will include enhancements specifically for the new Xbox One X console when it launches on November 7th. Halo 3, Assassin's Creed, Fallout 3, and The Elder Scrolls IV: Oblivion will all include tweaks that push the on-screen pixels to nine times more. Some games also have 10-bit color depth instead of 8-bit, and even HDR support.

Microsoft is using the Xbox One X Enhanced program to tag games with an “Enhanced” logo, which indicates the titles optimized for the new console. This doesn’t necessarily mean that 4K and HDR have been added, as there are separate logos for those features, but Enhanced means the game will run better on the Xbox One X on a 1080p or 4K TV.