Melasma is a condition evidenced by brown splotches or patches on the skin, often on the cheeks, forehead, bridge of the nose or upper lip.  Its actual cause is unclear, but it appears to be related to a number of factors, including hormonal changes, sun exposure, and contraceptives.   Melasma can be effectively treated with advanced lasers that penetrate deep enough to eliminate the cells causing the condition, but leave the surrounding healthy skin unaffected. 

Chemical peeling can also be effective at reducing Melasma.  Topical creams containing hydroquinone or kojic acid may lighten the dark pigmented spots.  Use of these should be monitored by a professional. 

As for freckling, though certain types of skin are more susceptible, the best way to prevent it is rigorous adherence to sun protection, including daily use of sunscreen.