I've noticed there are a LOOOOOT of artists on here, especially furry artists like myself, who have difficulty discerning the difference between these six common types of undergarments when drawing characters in "fancy clothing," so I've whipped up a handy diagram to make things easy to understand I didn't bother shading it since it's only for reference purposes.
Panties: Basically just frilly, tight underwear. Can be any colour or pattern.
Socks: This one should be obvious, but usually only go ankle-high and made with thick, opaque material. Can be any colour or pattern.
Stockings: Like socks, but much longer, usually going well up past the knees and stopping just bellow the hips. Usually made with thinner, lighter material that socks but still most often opaque. Can be any colour or pattern.
Leggings: Usually made with a thick, durable, stretchy material, are form-fitting and act like underwear that extends all the way down to the ankles. Can be any colour or pattern.
Tights (my personal favourite): Made with similarly thin but opaque (usually) material as stockings, but envelope the entire lower half of the body from toe to abdomen, acting as both underwear AND footwear. Can be any colour or pattern.
Pantyhose: Also known as "nylons", they're very similar to tights except EXTREMELY thin and usually transparent or translucent. Thicker around the hip-area for durability and form fitting. Most often black, grey, white, beige or dark brown, with a few exceptions. Do not usually have patters, save for specialty costume ones which may have fake tattoos or scars and stitch marks printed on them for Halloween or the "dark, edgy" types.
If you think I missed anything or got anything wrong, please don't hesitate to tell me. I hope this is helpful to all you fellow artists out there. :3