What are those?

Tonight Ellie and I were "talking" on her bed as we traced matchbox cars across the sheets. It's in those moments that real secrets are shared. Lying there propped up on my elbow... she asked, "Mama what are those lines going across your forehead?" I didn't say anything at first, more stunned at such a question. Wrinkles, I signed. She proceeded to describe how there were four long lines. Another sign. She wanted to know how I got them and if they'd go away. I mentioned something vaguely about growing older. Ellie is very inquisitive, so there were more questions to follow. She summarized by saying, "PawPaw has lots of wrinkles".