How is virtual host configured correctly?

I am installing apache
in linode. He has given me a domain name 123.456.123.123
to contact my var/www/html question
and can also display
normally, but I have opened another xxx.ccc.com
license 123.456.123.123 and xxx.ccc.com (also open https). Both var/www/html
problems can be found.

I now want to split into multiple sites on the same server
I want to be able to access var/www/html/ccc/

when I click xxx.ccc.com.

so I put a web fake xxx.php on ccc
when I set up multiple sites according to the website (https://codeshelper.com/q/10.

)

<VirtualHost *:80>
ServerName xxx.ccc.com
DocumentRoot "/var/www/html/ccc"
</VirtualHost>

I tell xxx.ccc.com he will go to / var/www/html (this is not what I want either)
when I use 123.456.123.123, the first session will be OK, but other directories will fail
but at this time I can open the 123.456.123.123/ccc/xxx.php account!
this is not right!
Why do you seem to have lost
what I want is to enter xxx.ccc.com to access / var/www/html/ccc/index.php, but the domain is like xxx.ccc.com
now 123.456.123.123/ccc/xxx.php can be downloaded, but I still need to add a directory?! If you are right, you can also input 123.456.123.123/xxx.php