Skim through

What it does: emollient, viscosity controlling, emulsion stabalizing 

Also called: palmityl alcohol 

The science

A fatty (the good, non-drying kind of) alcohol that does all kinds of things in a hair care product: it makes the skin and hair feel smooth and nice (emollient), helps to thicken up products, and also helps water and oil to blend (emulsifier). It can be derived from coconut or palm kernel oil.

Benefits for your hair

Promotes smoothness

Cetyl alcohol helps to smoothen the hair due to it being an emollient.

Prevents dryness

As an emollient, cetyl alcohol is considered an effective ingredient for soothing and healing dry skin. It's great at hydrating and moisturizing, too which helps to soften the hair.

Prevents tangles 

As it's hydrating, it provides good slip to help detangle hair.

TLDR 

Cetyl alcohol helps to smoothen and detangle hair, thicken and stabilize products, and prevent dryness.