Input/output completion port

Imagine you have a room with a lot of doors and you need to know when someone comes in or out of any of them. That's what an input/output completion port does for a computer program.

When a program needs to do something with a file or the internet, it uses a "door" called a handle to access it. The program can ask the input/output completion port to keep an eye on all the handles it's using, and let the program know whenever someone "comes through the door" by completing an action like sending data or receiving data.

This way, the program doesn't have to check every door all the time. Instead, the input/output completion port tells the program when someone is using a door, and the program can focus on doing other things until it gets notified.

Overall, an input/output completion port helps a computer program keep track of all the work it's doing with different files and internet connections, so it can efficiently handle multiple tasks and not waste resources constantly checking for activity.