Surfactant

A surfactant is a chemical that lowers the surface tension of a liquid. Less surface tension lets the liquid soak into things better, and can also let bubbles form easier. A liquid that bubbles and soaks into things is better at cleaning, so surfactants are used in soap.
Uses.
Every year, 15 million tons of surfactants are made. Half of them are used in soap; the rest are used in many different ways including making toothpaste and concrete.
One popular surfactant is sodium laurel sulfate, also called sodium dodecyl sulfate or SDS. SDS is a cheap, commonly used surfactant that is used in almost every toothpaste and many shampoos, body washes, and shaving creams.
Safety and environment.
Small amounts of most common surfactants are usually not harmful to people or animals, although if they get into eyes they can be painful. Very large amounts of surfactants can kill animals, but the amount varies depending on the surfactant.
Larger amounts of surfactants can be a problem in the environment, where they let the soil hold more water than usual, but this problem usually goes away in a few days.