What is a preamble? please

Match the vocabulary word with its meaning. 1. capitalism to change or improve something by correcting faults or removing abuses 2. chattel an economic system based on private ownership and competition motivated by profit 3. imperialism policy extending political, economic, or military rule over another 4. indentured an economic system where colonies supply goods to the mother country 5. mercantilism an agreement committing one person to be another's slave for a certain period of time 6. reform a type of slavery where the slave is the sole property of the master with no rights

Answer the questions in the image for zoom in to read : )

During the era of european expansion, what was the biggest reason for spain’s push for exploration?