A more thorough explanation:

The Transportation Security Administration (TSA) is a government agency that works to keep air, water, rail, and highway transportation safe and secure. It was created after the terrorist attacks on September 11, 2001, and is now part of the Department of Homeland Security.

For example, when you go to the airport, TSA agents check your bags and scan you with metal detectors to make sure you're not carrying anything dangerous. They also screen passengers to make sure they're not a threat to the safety of the flight.

Another example is when you go through a security checkpoint at a train station or bus terminal. TSA agents may search your bags and ask you questions to make sure you're not carrying anything that could harm others.

Overall, the TSA's job is to make sure that transportation is safe and secure for everyone who uses it.