url.md: clarify

- the specified URL can also get data sent to it
- rephrase the scheme guessing part
- mention target options for each URL for saving data
- mention --remote-name-all
- remove "warning" and make it into normal text

Closes #15396

docs/cmdline-opts/url.md

@@ -16,17 +16,19 @@ Example:
 
 # `--url`
 
-Specify a URL to fetch.
+Specify a URL to fetch or send data to.
 
-If the given URL is missing a scheme name (such as `http://` or `ftp://` etc)
-then curl makes a guess based on the host. If the outermost subdomain name
-matches DICT, FTP, IMAP, LDAP, POP3 or SMTP then that protocol is used,
-otherwise HTTP is used. Guessing can be avoided by providing a full URL
-including the scheme, or disabled by setting a default protocol, see
---proto-default for details.
+If the given URL is missing a scheme (such as `http://` or `ftp://` etc) curl
+guesses which scheme to use based on the hostname. If the outermost subdomain
+name matches DICT, FTP, IMAP, LDAP, POP3 or SMTP case insensitively, then that
+protocol is used, otherwise it assumes HTTP. Scheme guessing can be avoided by
+providing a full URL including the scheme, or disabled by setting a default
+protocol, see --proto-default for details.
 
-To control where this URL is written, use the --output or the --remote-name
-options.
+To control where the contents of a retrieved URL is written instead of the
+default stdout, use the --output or the --remote-name options. When retrieving
+multiple URLs in a single invoke, each provided URL needs its own dedicated
+destination option unless --remote-name-all is used.
 
-**WARNING**: On Windows, particular `file://` accesses can be converted to
-network accesses by the operating system. Beware.
+On Windows, `file://` accesses can be converted to network accesses by the
+operating system.