When a regular website is visited through Tor Browser, Tor protects/anonymizes you as a user.
If a website is hosted at an onion address, the web server is also protected by Tor, the same way as you are.
Not really. It’s more similar to if the webserver was connected to the internet through a VPN with it’s HTTP(S) port forwarded through the VPN. You connect to the VPN’s IP address, which forwards to the webserver’s IP which stays hidden. And you yourself are also connected to the internet through a (separate) VPN. Now, instead of a VPN connection, both you and the webserver are connected to the internet through Tor circuits.
This video does a good job of explaining how it works.
What is difference between onion and just regular for?
for is a loop type used in programming onion is a type of a hidden website
When a regular website is visited through Tor Browser, Tor protects/anonymizes you as a user. If a website is hosted at an onion address, the web server is also protected by Tor, the same way as you are.
Is it kind of like having a proxy and a reverse proxy?
Not really. It’s more similar to if the webserver was connected to the internet through a VPN with it’s HTTP(S) port forwarded through the VPN. You connect to the VPN’s IP address, which forwards to the webserver’s IP which stays hidden. And you yourself are also connected to the internet through a (separate) VPN. Now, instead of a VPN connection, both you and the webserver are connected to the internet through Tor circuits.
This video does a good job of explaining how it works.