Which skin condition is characterized by the presence of brown spots?

Freckles are small, brown spots that typically appear on the skin, especially in areas exposed to sunlight. They are a common and benign condition associated with the overproduction of melanin, the pigment responsible for skin color. Freckles tend to be more prevalent in individuals with lighter skin and can become more pronounced with sun exposure.

In contrast, vitiligo is characterized by patches of skin losing their pigment, resulting in lighter spots, which is opposite to the brown spots seen in freckles. Psoriasis is an autoimmune condition that leads to red, scaly lesions rather than brown spots. Acne is characterized by pimples and blemishes, which do not resemble the brown spots noted in the question. Thus, freckles uniquely match the description of being marked by the presence of brown spots.