Imagine you and your friends are drawing pictures together. You each have a piece of paper and some crayons. Your teacher has set a rule that you can only draw one line at a time and then you must pass the paper to the person next to you. This way, everyone gets a chance to draw and nobody gets left behind.
This is kind of like how TCP pacing works. TCP (which stands for Transmission Control Protocol) is a way for computers to send information to each other over the internet. In order to make sure that everyone gets a chance to send information and nobody gets left behind, TCP pacing slows down how quickly a computer can send data so that it matches the speed of the computer it is sending the data to.
Just like passing the paper to your friend after drawing one line, TCP pacing makes sure that each computer only sends a certain amount of data before waiting for a response from the other computer. This prevents any one computer from overwhelming the other computer with too much data all at once.
Overall, TCP pacing is a way for computers to communicate with each other in a fair and controlled way, so that everyone gets a chance to participate and nobody gets left behind.