Ha, I guess I think of them as somewhere in between. You wouldn't wear a pair of pantyhose/nylons/whatever your word for them with just a long tunic, but you might a pair of good leggings. I don't have any long tunics or anything so I tend to wear mine under shorter dresses or skirts.
I was at H&M the other day and one of the employees was sporting a pair that they carry right now that look like denim. She had on a long tunic (belted I think) and the leggings were tucked into spring-y boots. I liked the look. They may have had other colors there, too. I can't seem to figure out their sizing, though...I was swimming in some things or sausaged in others (I'm a 16). Trial and error, there!
If you find a good pair, let me know!