What causes freckles and pigment moles?

The Sun! Freckles are a way our skin tells us: "Hey, I'm getting damaged by the sun!" What is happening is that the pigment producing cells in the skin, called melanocytes feed melanin to the keratinocytes, the normal skin cells that form the outer barrier of our skin to protect us. It keeps the good stuff in and the bad stuff out. When the melanocytes in the skin get damaged by the sun, we produce freckles which are abnormal collections of melanin pigment, packaged in a different way than a normal melanin pigment is packaged. They sit on the top layer of our skin which is called the epidermis.

http://www.freckles.org/whatcausesfreckles.html