Lasers are used in cosmetic procedures for everything. From skin resurfacing, to teeth whitening, to liposuction, and even for vision correction. All lasers are either ablative or non-ablative. Ablative lasers remove the top layer of your skin and treatments typically require some recovery time while the skin heals. Non-ablative lasers are less invasive and use heat to stimulate cells to thicken the underlying collagen resulting in improved skin tone and elasticity.
Dark spots are the result of excess melanin production in a concentrated area. Some birthmarks are caused by high skin pigmentation, and other forms of dark spots (e.g. age/sun spots) occur when the skin produces higher levels of melanin in response to sun exposure. This is how the skin tries to protect itself since melanin is like a type of sunscreen that your body produces.
Laser treatment for age spots should effectively minimize spot appearance and leave no scars.
Disclaimer: Results may vary from person to person