ELI5: Explain Like I'm 5

Middlebox

Alright kiddo, let me explain to you what a middlebox is.

Imagine you want to send a toy car to your friend who lives in a different city. You put the toy car in a box and send it through the post office. Along the way, the box goes through many different machines and people who make sure it gets to your friend's house.

A middlebox is like one of those machines in the post office. It sits in the middle of the path that your toy car (or in this case, your internet traffic) takes on its journey to its destination. It's called a "middlebox" because it's in the middle of the communication path between two devices on the internet.

Middleboxes can do different things to your internet traffic. Some of them help with security, like a firewall which blocks bad guys from accessing your computer. Others help with performance, like a proxy that caches frequently requested information so it can be sent to you faster. Some middleboxes might even change your internet traffic in some way, like changing the format of a video or compressing images to save bandwidth.

Basically, middleboxes are like helpers along the way that make sure your internet traffic gets to its destination safely and quickly. They do this by inspecting and modifying the traffic as it passes through them. But just like how you need to trust the post office workers to get your toy car to your friend, you also need to trust the middleboxes to handle your internet traffic properly.