What were the two main reasons Spain sent expeditions to the Americans?

Answer 1

There were actually THREE main reasons that Spain sent expeditions to the America. In English these are usually summed up as: Gold, God, and Glory.

Gold: There were impressive, untapped Natural Resources in New World, especially gold and silver, which were extensively mined and brought vast riches. There were numerous other natural resources that abounded in the Americas, such as fish-stocks and lumber (which were mostly depleted in Europe) as well as new foods like the potato, tomato, pepper, maize, sweet potatoes, squashes, etc. that led to a population boom in Europe.

God: Spaniards believed fervently in their God and proselytizing Catholicism. When it was discovered that there were millions of unconverted souls in the New World, Spain invested huge amounts of resources to send missionaries to the New World to bring these people to Catholicism. Similarly, Spain imposed a ban on Muslims and anyone suspected to have Muslim roots (the Moriscos and Berberiscos) from going to the Americas based on the fear that Islam could spread there and create a new set of holy wars just like Spain had just fought in the Reconquista.

Glory: Individual Spaniards could obtain renown or personal wealth by coming to the New World and discovering new areas or civilizations in the New World. This kind of social prestige was incredibly valuable.