Okay here it goes. Every website in the internet is hosted on one or more servers. These servers all have an IP adress which makes them unique and eays to identify. But you can imagine it would be quite annoying to remember all these IP adresses and enter them into your browser instead of the name. Try it out. Enter 172.217.22.100 instead of google and you will get to the google website too.
So to make lives for us easier there are DNS servers mostly run by the Internet providers. DNS stands for Domain Name Server. There are tables in which all these relations are stored. So they know when you enter google.com they have to go to 172.217.22.100
And that is where the provider will implement their protection or blocking. When there is no or a wrong IP associated with the adress you enter you won't get there.
The solution is now to use independent DNS servers who do not censor things. Here is a list of independent DNS Servers: https://wikileaks.org/wiki/Alternative_DNS
When you tell me the type of your router I can help you further how to change it.