Harem pants, which originated in India, are like a cross between a skirt and a pair of skinny jeans. The legs, from the knees down, are fitted. The crotch area is loose and baggy as if it were cut to be a skirt. Traditional harem pants can be extremely large and baggy, with a very wide and full fit, very roomy, loose fitting, over-sized, puffy, spacious, with elastic in waist and at ankles, and with the crotch below the knee almost to the ground.
Harem pants are commonly worn with a pleated skirt — a short skirt that covers the top portion of the harem pants. Both harem pants and pleated skirts are commonly used in belly dancing. There are resources that show various forms of pleated skirts and explain how they are created.
They’ve also emerged as a “modern” version of harem pants made popular in the late 1980s by MC Hammer and thus known as hammer pants. They are intended to be made more fashionable and require less fabric.