What import restrictions could be placed on imported items?

What import restrictions could be placed on imported items? Why is volume important to an import? Why should an importer be aware of any laws that may affect purchase? What is an export quota? What is a customs broker? What is a Port of entry? What is a deferred duty program? What are terms of purchase? What is a confidentiality and non-disclosure agreement? What is a consignment and what are the potential benefits of this type of transaction? what is the CBP, and what are its mission and purposes?