Among "sporting goods" there are lots of different lines that are used for catching fish or sea life.

But the most-typical thing called "fishing line" is better described as monofilament. It is very strong extruded plastic. It's a good line for bead storage--but not necklace-making. Eventually it will become brittle and will break. Plus it does not have good "drape."

Structured lines are much better for strength and drape.

Lines can be twisted-together, or braided together. Nowadays that are lots of very fine strong braided lines.

At Facebook, one of my friends recently told me about an exceedingly fine fishing line call "Frog's eyelash." Imagine how fine that must be!