These spots on your hand can come from a vareity of sources such as too much exposure to the sun, specific medications, pregnancy, trauma or the most common cause which is normal aging.
Sun exposure, diet, climate, or aging or a combination of all. Your hands are the most exposed parts of your body regardless of weather and take the most environmental damage.
Those are age spots. They are caused by sun damage. You can buy creams and peels to lighten them. You will need to use sunscreen everyday to prevent new ones.
They are more than likely age spots. As you age you will see spots like this. It is your skin pigment darkening from sun exposure and is more than likely nothing serious. If you feel that it might be, see your doctor for a check up.
Most of these kind of spots are caused by sun exposure. Also called age spots, sometimes they appear when a person gets older due to skin thinning. There are topical creams that supposedly remove them.
