Think of an oil cargo ship. A huge ship carrying oil travels the Atlantic ocean, and ends up in a city port. The oil is pure.

Mobil comes to the port and picks up some oil and brings it to a local town. They put in their own additives to the oil. Another oil company comes and puts in their own additives and brings it to another town.

All the houses in the first town gets their oil from Mobil, who has put their own mix into the oil. The other town gets the other oil.

Some towns end up with cleaner, more energy efficient oil because of the additives. Other towns end up with crappy dirty oil.

Now translate this to different countries getting Internet access. A cable goes across the ocean. The Internet is the oil. Countries get the Internet (when the cargo ship carrying the oil lands in a port), and add their own filters (as some countries block various Internet content). Different ISPs get the filtered Internet connection, and then it gets delivered to the houses depending on what ISP they use.