The rivalry (in the 16th century) concerned the issue of which country could claim and exploit which part of the newly discovered Americas and other parts of the world newly discovered or yet to be discovered.
The issue was settled by mutual consent by the Pope, who divided the map of the world in a Spanish and a Portuguese sphere of influence and colonization, where the other party had to stay out of.
Portugal and Spain
Portugal is west of Spain, between Spain and the Atlantic Ocean.
Portugal is bounded by the Atlantic Ocean and by Spain.
Spain is the only country that borders Portugal.
Spain wished to compete with Portugal for trade. (Apex)
Portugal
Portugal and Spain
Spain is known as Spain and Portugal as Portugal.
Portugal is west of Spain, between Spain and the Atlantic Ocean.
Spain and Portugal both sponsored him
Portugal is bounded by the Atlantic Ocean and by Spain.
Portugal is west of Spain.
Spain is the only country that borders Portugal.
Portugal is west of Spain.
Spain wished to compete with Portugal for trade. (Apex)
Spain extends both farther north and farther south than Portugal does.
Spain borders Portugal along the west side and France on the north.