To break it down for you, a chad refers to the piece of paper that is created from punching a hole. In politics, it is a tiny bit of paper that is punched from a ballot using a punch-type mechanical voting machine
A hanging chad is when the chad does not completely detach from the paper, in which case, the vote may not be properly counted.
In 2000, many of the Florida votes were used by this style of voting and caused issues in an already contentious race.
Not only that, a “hanging chad” makes a great Halloween costume. Remember when Ted from How I Met Your Mother wore this costume many years in a row?