distinctions among the real estate contract, a deed, and a mortgage

What are the distinctions among the real estate contract, a deed, and a mortgage, and how did these legal concepts play a leading role in the real estate crisis in the United States? (based on Legal Challenges text Chapter 16)

2. What makes a covenant not to compete legally valid and enforceable in a contract for the sale of a business? What additional requirements make such a covenant enforceable against an employee in an employment contract situation? (based on Legal Challenges text Chapter 17)

3.How has the law in the United States caught up with technology when it comes to the making of contracts? (based on Legal Challenges text Chapter 18)