Black jeans refer to a type of denim pants that have been treated with a special process to create a dark, almost black appearance. This is achieved through a combination of indigo dye and a chemical treatment called "stonewashing," which involves sandblasting or tumbling the fabric in small stones to create an aged, worn-in look. Black jeans are popular for their stylish and edgy appeal, as well as their versatility - they can be dressed up or down depending on the occasion.