What does having cafe-au-lait spots signal?

Coffee spot. These are flat, well defined pigment patches that may not be evident at birth. A few <6 and < 1cm size at puberty are likely unimportant.They are common in the general population as benign but permanent findings. In greater numbers and larger size they may indicate a form of neurofibromatosis (there are several). Your dr can sort out your specific issue with after an exam & family history.
Neurofibromatosis. Cafe-au-lait (french=coffee with milk) spots are tan patches at least 1cm. Multiple such spots occur in hereditary neurofibromatosis or von recklinghausen's or (erroneously) "elephant man's" disease". Other signs include nerve cell tumors neurofibromas(soft, fleshy, skin-colored, grouped papules, nodules, tumors), armpit freckles, and benign &/or malignant acoustic (8th cranial nerve) neuromas.