When salon professionals use the term "cuticle hair," they're usually referring to something like a hair extension or a remi hair weave. It's just one of those terms people use without thinking much about where it comes from. But have no fear: Cuticle hair isn't some special kind of hair -- it's simply a set of extensions.

But why call it cuticle hair? After all, aren't cuticles and hair two totally separate things? And aren't cuticles part of your fingernails? Sure they are -- but every strand of hair on your head also has a cuticle.

Cuticles and hair go together sort of like skin and muscle. In fact, a cuticle is hair -- it's just the outside part of the hair.

A strand of hair is composed of three separate layers: The cuticle, the cortex and the medulla.

Cuticle. Hair shafts have a layer of flat cells on the outside, that overlap like roofing tiles and protect the inside of the hair shaft from damage. You can actually feel the cuticle by grasping a strand of hair by the tip and running your fingernail along it, from tip down to root. Hair feels rougher and more coarse this way, because you're running "against the grain," and hitting the ridges of the cuticle cells one by one.

Cortex. Unlike the cuticle, hair at the cortex level is softer and more elastic. The cortex is actually a strand of proteins that resembles a telephone cord, or the wire spiral that holds a notebook together.