Why are some frameworks (e.g. Flask for Python, Sinatra for Ruby) called microframeworks?
What differentiates them from full-fledged frameworks, like Django or Rails?
It's a shorthand for "framework written by someone annoyed by established farmeworks' percieved excessive complexity, which is going to gradually accumulate a similar amount of complexity proportional to its growth in popularity as it's extended to handle more varied requirements."
This link should provide you with all the info you need (in terms of Flask)...
Extract from the same link:
I hope that makes it clear. :)