According to DermNet NZ, the medical term for a freckle is ephilis. Freckles form after pigment is accumulated in the skin from sun exposure. Fair-skinned people tend to have more freckles on their bodies than dark-skinned people do.
DermNet NZ also states that melanin, the pigment that gives a freckle its brown color, is made from melanocyte cells. Freckles are most abundant in the summer, when exposure to the sun is at its highest, and they fade or disappear during the winter as skin cells are replaced. There is no treatment needed for freckles, but limiting sun exposure can reduce them.