Localhost is actually your loopback address which resolves to 127.0.0.1
and this is only accessible from your PC. I think what your trying to ask is to allow IP's from your subnet to access certain directories but not others. If thats the case then to do this you will need to edit your httpd.conf and find the <Directory>
section. The below example shows you how to enabled access from any PC with an IP from 192.168.1.0/24 (1-254) and localhost (127.0.0.1) to the following path /var/www/sub/folder/
then deny all.
<Directory /var/www/sub/folder/>
Order allow,deny
Allow from 192.168.1.0/24
Allow from 127
</Directory>
As you can see it firstly allows all from the the config and then deny's everything else. If you wanted access for just your local PC then you would do something like this:
<Directory /var/www/sub/folder/>
Order allow,deny
Allow from 127
</Directory>
This will only allow 127.0.0.1 (Localhost) to access the folder.
You can add multiple Directory settings within the httpd.conf for specific folders, just make sure you restart Apache for the changes to apply.