A Browsable Slideshow is in an interactive framework for the user to navigate still images of galleries or text information. Still images may be presented and changed without interruption to audio playback.

Still Images

Still images on Browsable Slideshows are often use the MPEG-2 format (using the Primary Video layer) as it's similar to JPEG when it comes to realistic photos.

Example of a Browsable Slideshow using interactivity to navigate the still images with an remote. (Iria: Zeiram the Animation)

Uses

Browsable Slideshows are often used for showing off photo and art galleries of a movie, or to provide text information such as a script for the user to read. 

However, some studios such as Lionsgate and Shout don't use BD's Browsable Slideshow framework but instead use a normal playable video, this makes navigation between different pages a little tedious.

Example of a Browable Slideshow showing the first draft script of Aliens

Timebased Slideshow for UltraHD Blu-ray

Browsable Slideshows is not supported on UltraHD Blu-ray, but it does support Timebased Slideshows, a successor. Timebased Slideshows are basically the same except it uses AVC IDR I-frame or an HEVC IDR I-frame for still images. HEVC provides 2160p UHD images, AVC only provides 1080p HD images.