Mostly it's about various black artists and civil rights activists from the Civil War Era, then the Harlem Renaissance, then the 50s-60s civil rights activists.
They'll usually have a black history category on Jeopardy. And cable will carry important movies and such. It's also a marketing opportunity. Nike etc. will release Black History Month products with African-themed patterns and whatnot.
It's become like one notch above "National Talk Like a Pirate Day". Most black people I've ever mentioned it to or overheard conversations with use it as a punchline and it's largely just an excuse for corporations and government entities to feign interest in cultural diversity and black issues. Not that those are bad things to be interested in... it's just laughably phony when it's coming from American corps.
People joke about it, but in a country where white people could own black people 150+ years ago, it definitely helps sow some harmony, I would like to think.
Alabama didn't want to give a black man who fought for equal rights as whites his own holiday, so they paired him up with a white man who fought against the United States for the right to own black people.