What is a weapon of mass destruction (WMD), and what does chemical, biological, radiological, nuclear, explosive (CBRNE)

Question:

What is a weapon of mass destruction (WMD), and what does chemical, biological, radiological, nuclear, explosive (CBRNE) have to do with WMD? What are the Centers for Disease Control and Prevention's (CDC) role and mission in protecting the country from a CBRNE attack?