The positive effects include Portugal discovered new lands, sea routes, and made new maps of the earth. Vasco de Gama found the route to India, where they could trade spices and gold. The trade made the country rich. Explorers were able to find a conquer new lands.
The negative effects include them enslaving many Africans along the way, and disrespecting natives. This caused them to ignore the culture and a lot of unneccesary deaths occured. Portugese explorers made Brazilians suffer until they caved into converting to Christianity, and explorers also attacked and killed any Muslims they encountered.