What are economic resources, and how does scarcity of resources apply to economic decisions?

What are economic resources, and how does scarcity of resources apply to economic decisions? Think of a business firm you recently visited (such as Walmart, Home Depot, Red Lobster, Barnes & Noble, McDonald's, etc.). What motivated the producers of each of the products in the store to make these and offer for sale? How did the producers decide on the best combination of resources to use for producing each product? Who made those resources available, and why? How does the market determine who will get the goods and services? Who decides whether these particular products should continue to be produced and offered for sale? How do these decisions differ between capitalist and socialist systems?