It is very different from video, in my mind. Video places emphasis on visuals, where for many lectures or meetings the audio is where most of the content is. By only talking photos or short videos at the points in time where the visuals are important you cut down on a lot of excess information that will need to be searched through later. In a way, the photo are essentially bookmarks into your audio.
If I was looking back on a hour lecture that had 15 slides, it'd be much easier to tap the photo of the relevant slide and listen to surrounding audio rather than scrub through a hour of video to find it.
Additionally, taking video requires being able to position my phone properly for the entire duration of recording. I don't know how my profesor's would respond to me setting up a mini tripod during lecture. I do know they don't care if i snap a picture of a slide or whiteboard every once in a while.
Finally, photos capture the content in higher quality then videos can, which often is very important.
Otherwise known as a "video". :)