"Push" and "pull" factors are usually associated with immigration. "Push" factors are the things that propel people to leave a place (religious persecution, economic downturn, famine) and "pull factors" are the things about a place that make people want to go to a place. These include cheap land, more freedom, and other factors. The factors that "pushed" European nations to explore were mostly economic in nature. They were especially interested in discovering a water route to Asia in order to monopolize the spice trade. They also became involved in exploration as a matter of geopolitical competition that reflected the state of affairs in Europe. What was appealing about colonies (remember that exploration and colonization were two different things) was also economic in nature. Under the economic philosophy of mercantilism, European powers attempted to develop favorable balances of trade with their colonies. They exploited resources (beaver pelts, timber, and precious metals, or example) and cultivated cash crops (sugar, tobacco, and coffee, for example). They also used colonies as outlets for domestic goods. European nations saw colonies as outlets for expanding populations as well, and in Spain especially, there was a powerful desire to convert Native peoples to Christianity.