Meaning of “the nitty-gritty” - Learner’s Dictionary

the nitty-gritty

noun uk us /ˌnɪtiˈɡrɪti/

the important details of a subject or activity:

English teachers should concentrate on the nitty-gritty of teaching grammar.

(Definition of “the nitty-gritty” from the Cambridge Learner’s Dictionary © Cambridge University Press)