Cryptic description for download GETINFO options

Hi there, descriptions for the recent spec addition are pretty cryptic...

"The serialized download status for the FLAV_MICRODESC consensus for whichever bootstrap state Tor is currently in."

I expect this description only makes sense to the feature's author. What is FLAV_MICRODESC? What does this 'serialized download status' mean? Since it discusses 'bootstrap state' I'm guessing this is only relevant when tor is first starting up (showing percentages complete)?