From Diablo Wiki
The lore window displays story and lore information for everything in Diablo III. Icons for Latest Quest, World, People, Beastiary, and Tutorial Page are visible down the left side of the window, with informative entries for each of those visible in the main window.
The Lore window was first seen in the BlizzCon 2010 demo, where it was nifty, but unpopulated. The icons were there, but no text entries were present as of yet. The feature was clearly new, but it is hoped the developers have continued to flesh it out since then. The feature is present in the Diablo III beta build, though not yet described in detail.
The Lore window is accessed via a tab on the Quest window.
Diablo III Interface elements:
- The Belt Interface.
- Skills and traits window
- The Artisans window.
- Quests window
- Lore window
Lore Window Interface
The lore window was first seen at Blizzcon 2010, which is the source of the (blurry photo of a monitor) image here. Much better images should soon be available from the Diablo III beta build.