PF (firewall)

A "firewall" is like a security guard that helps protect your computer or network from bad things on the internet.

Imagine your computer is a house, and the internet is a street. The firewall is like a big fence around your house that only lets certain things come in or go out.

One of the things the firewall does is check who is knocking on your door (trying to access your computer). It looks at the information coming in and decides if the person knocking is a good friend (safe) or a stranger (potentially dangerous).

The firewall also looks at the things you are sending out from your computer. It makes sure that you are not accidentally sending out personal information (like your address or credit card details) to someone who shouldn't have it.

But the firewall doesn't just let anyone in or out. It has rules that it follows to decide who is allowed through the fence. These rules can be like a checklist. For example, only let in people from a certain list of approved friends, or only let out certain types of information.

The firewall also keeps an eye out for any suspicious activity. If it notices something strange or unsafe, it can block it from entering or leaving your computer.

In summary, a firewall is like a security guard for your computer or network. It checks who is trying to get in or out, follows rules to allow or block certain things, and keeps an eye out for anything that could be harmful.