It's not a place you go, as in putting it in your address bar. It's what you put in your router for primary DNS (Domain Name Server). DNS decodes text (Whatever.com) into the numeric address the Internet needs. If the name server your router is using gets corrupted or goes down, you can switch to a different DNS or use the website numeric address directly if you know it.
If there's a website that is mission critical to you, it's a good idea to know the numeric address in case you can't find a working DNS, such as might occur during a cyberattack aimed at DNS servers.
Thank you for taking the time to explain.