Is it normal for the vaginal openeing to be be covered?

Is it normal for the openeing of the vagina to have a little skin covering it? I'm not talking about either the labia majora, labia minora or hymen. The opening on my vagina is covered by a thin bit of skin that doesn't hurt when it's pulled. I'm also not a virgin so I know it's not the hymen. Also, when I push down on the muscles the skin parts exposing the opening. Anyway, is this covering normal, or should the vaginal opening be like a wide open hole once the labia minora is parted?