Homeland Security: This is a specific department in the U.S government responsible for protecting the country within and beyond its borders. Its wide-ranging duties include aviation security, border control, emergency response and cybersecurity.
Foreign Policy: This term refers to strategies that a government uses to interact with other countries. It's like the rules and guidelines set by parents about who their children can hang out with after school.
Cybersecurity: This is the practice of protecting internet-connected systems such as hardware, software, and data from digital attacks. It's akin to having antivirus software on your computer; it helps protect your personal information from being stolen by hackers.