The type of ship developed by the Portuguese for long voyages of exploration was the caravel.
Caravels were relatively small, fast, and highly maneuverable sailing ships that became central to Portuguese exploration during the 15th and 16th centuries. Their shallow draft helped them operate near coasts and in rivers, while lateen, or triangular, sails allowed them to tack more effectively than many earlier vessels. These qualities made them valuable for probing unfamiliar Atlantic waters.
The design developed gradually from Iberian fishing and coastal craft rather than appearing as a single invention. Early caravels were small and often had one mast; later versions could have two or three masts. Portuguese sailors used them along the African coast, and Spanish expeditions, including Columbus’s, also employed them.
Caravels were excellent exploration vessels but had limited cargo capacity. For heavily loaded trade voyages, larger ships such as carracks, also called naus, became more useful. Columbus’s Pinta and Niña were caravel-type ships, whereas his flagship, the Santa María, was a larger carrack. That distinction is why the answer is not “galleon” or “frigate,” which belonged to later or different naval traditions.