glyceryl acrylate/acrylic acid copolymer

A common polymer (big molecule from repeated subunits), namely polyacrylic acid (aka carbomer when it comes to cosmetics) with glycerin attached to it in some places.

This polymer forms a hydrogel that helps deliver moisturizing, water-soluble ingredients such as glycerin to the skin. Think of it as a very thin, wet sponge that a cosmetic manufacturer can fill with good ingredients for your skin. It also works as a thickening agent with slippery feel and can draw water to the skin, providing skin hydration.

Also, don’t let people scare you into thinking polyacrylic acid is dangerous because of the toxicity of acrylic acid. Since acrylic acid is dangerous due to its ability to absorb into the skin (since it’s small), when you chain them together into a polymer (which is big), this danger is no longer significant. EWG Learn more.