One of Donald Trump's first picks for his new administration was to choose Steve Bannon as his chief White House advisor (one of the two most powerful position in the administration -- along with Chief of Staff).
The pick has received a lot of criticism, even from Republicans -- because Bannon was formerly the head of Breitbart News (an ultra-right-wing website that promoted racist and white supremacist ideas). He has also been quoted as making disparaging remarks about minorities, muslims, and women. As bad as that is, and it is very bad, he may actually have done worse. He may have shown himself to be a criminal by breaking campaign laws (felonies).
It certainly looks like Bannon broke campaign law in three different ways -- 1) by receiving money from a super-PAC while working for the Trump campaign, 2) by not fulfilling the legal waiting period when going from a super-pec to working for a campaign, and 3) by coordinating with a super-PAC while working for the Trump campaign.
The charges have been brought by the political watchdog group, The Democratic Coalition. They have filed an official report with the Federal Bureau of Investigation (FBI), requesting an investigation. Here is the statement from The Democratic Coalition explaining why they filed the FBI report: