Imagine you and your friends all have different gifts that you want to show each other. One friend can do magic tricks, another can draw amazing pictures, and another can dance really well. In order to show your gifts to each other, you need a special stage where you can perform and an audience to watch you.
Now, imagine if each of you had to pay different amounts of money to use the stage and have an audience. The friend who can do magic tricks might have to pay a lot of money because their performance is really popular and a lot of people want to watch. The friend who can draw amazing pictures might have to pay a little less because their performance is still popular, but not as much as magic tricks. And the friend who can dance really well might have to pay the least because their performance is not as popular as the others.
This is kind of how tiered internet service works. The internet is like the stage, and different websites and online services are like the performances. Some websites and services are really popular and have a lot of people using them, like Netflix for watching movies or YouTube for watching videos. These popular websites have to pay a lot of money to make sure their performance is available to everyone and doesn't slow down.
Then there are other websites and services that are not as popular and don't have as many people using them. These websites might have to pay less money because they don't need as much stage space or as big of an audience. They still get to perform on the internet, but they might not be as fast or easy to access as the popular websites because they don't have as much money to pay for it.
So, depending on how much money a website or service can pay, they get different levels of access to the stage of the internet. The popular websites get better and faster access, while the less popular websites might be a little slower or harder to reach. This is called tiered internet service.