In IP-based virtual hosting, you are running more than one web site on the same server machine, but each web site has its own IP address. In order to do this, you have to first tell your operating system about the multiple IP addresses. See my post on configuring multiple IP addresses on a single NIC . You also need to put each IP in your DNS, so that it will resolve to the names that you want to give those addresses .
In Name-based virtual hosting, you host multiple websites on the same IP address. But for this to succeed, you have to put more than one DNS record for your IP address in the DNS database. This is done using CNAME tag in BIND. You can have as many CNAME(s) as you like pointing to a particular machine. Of course, you also have to uncomment the NameVirtualHost section in httpd.conf file and point it to the IP address of your machine.