Here is a somewhat simplified explanation
When you are registering a domain you are essentially just creating a NS record:
mydomain.com NS <nameserver ip or name>
Then when a resolver is asked a question like what is the A record for myserver.com it goes and asks the tld server (.com) what is the NS record for mydomain.com. the tld then responds with the nameserver ip. Then the resolver will query the nameserver directly for the A record of mydomain.com
In practice there is a ton of caching going on here, but that’s the broad strokes
cmnybo@discuss.tchncs.de 14 hours ago
The DNS authoratative servers are what hold all of the records for your domain. With Cloudflare, you are stuck with theirs. As for why you want to use a different one, maybe you need more than the 200 records Cloudflare limits you to. Maybe you don’t like the way their API works for automating updates. Maybe you don’t want to set up all of your records all over again if you transfer your domain to another registrar. Maybe you just don’t like Cloudflare.
wltr@discuss.tchncs.de 13 hours ago
Thanks! Now it’s a bit more clear now.
To contribute to the discussion, I remembered that with Squarespace (my previous registrar), I had unlimited redirects, which I used heavily. I am not really sure about the unlimited part, perhaps that was hidden somewhere in the interface, and they have limits, and I just never saw them. But I remember Cloudflare communicated I have like 10, so I decided to not use it for nice-to-have but not really needed things. E.g. I used a subdomain for a blog, and created redirects for typical misprints in my name. Was handy, but not really needed. I should have document this, but I was too busy at the time, and now, almost a year later, I don’t really remember. There were differences with Cloudflare and Squarespace.