Wrinkles are lines which form on someone's face as they grow old.

When someone's skin wrinkles or when something wrinkles it, lines start to form in it because the skin is getting old or damaged.

A wrinkle is a raised fold in a piece of cloth or paper that spoils its appearance.

If cloth wrinkles, or if someone or something wrinkles it, it gets folds or lines in it.

When you wrinkle your nose or forehead, or when it wrinkles, you tighten the muscles in your face so that the skin folds.