What does "something 101" mean? [closed]
Solution 1:
It means "introductory something". The allusion is to a college course with the course code 101, which in the American system and probably others indicates an introductory course, often with no prerequisites.
Solution 2:
It means:
(chiefly US, postpositive) Basic, beginner, starting from scratch.
Geology 101 tells us that you can't build a reservoir on sandstone.
Source.