Quoting their changelog:

Camera

• General improvements for system stability and performance in certain conditions (Pixel 8 Pro and Pixel 8)

Display & Graphics

• Fix for display getting corrupted in certain conditions (Pixel 8 Pro and Pixel 8)
• Fix for issue with outer display in certain conditions (Pixel Fold)

Framework

• Fix for stability or performance with certain third party apps (Pixel 5a (5G), Pixel 6, Pixel 6 Pro, Pixel 6a, Pixel 7, Pixel 7 Pro, Pixel 7a, Pixel Fold, Pixel 8 and Pixel 8 Pro)

Wi-Fi

• General improvements for Wi-Fi stability and performance in certain conditions (Pixel 8 Pro and Pixel 8)

They also fixed a few CVEs (including one critical): https://source.android.com/docs/security/bulletin/2024-02-01