It adds new features and support for display of lock-screen content. The recent update for MSN Health & Fitness & MSN Weather had added Lock-Screen display support, and with current Glance update, you can see all the info on Glance screen.
Though changelog is not provided, here is what I noticed,
Name changed to Glance screen
Support for Lock-screen content display
Background app support
MSN Health & Fitness & MSN Weather info display is working
Option to hide Glance screen under night mode
Not all Lumia devices support Glance screen, so it is applicable for only those devices, which support this features.