URLs offer a fragment part. That is usually seen as a hash symbol (#) and a
name for a specific name within a webpage in browsers. An example of such a
URL might look like:
https://www.example.com/info.html#the-plot
curl supports fragments fine when a URL is passed to it, but the fragment part is never actually sent over the wire so it does not make a difference to curl's operations whether it is present or not.
If you want to make the # character as part of the path and not separating
the fragment, make sure to pass it URL-encoded, as %23:
curl https://www.example.com/info.html%23the-plot
The fact that the fragment part is not actually used over the network can be taken advantage of when you craft command lines.
For example, if you want to request the same URL from a server 10 times, you can make a loop and put the loop instruction in the fragment part. Like this:
curl https://example.com/#[1-10]