When you want to connect to your DVR remotely, you will need to use either the internal or the external IP address. This will be determined by whether you are accessing the DVR from inside the network or from outside the network. If you are accessing the DVR from inside your network then you will use the internal IP address. The internal IP address will usually begin with 192.168.XX.XXX . No port number would be used since you are connecting internally. The internal IP address can usually be found in your DVR under network settings.
To access your DVR from outside the network, you will need to use an external IP address followed by the port number to identify the DVR (unless you put the DVR on port 80). An external IP address is the IP address used to connect to your router. The port number will identify the individual device inside the network you wish to access. So an external IP address would not have 192.168 in the beginning but it could be anything else. An external IP address would be entered as XXX.XXX.XXX.XXX:port#
Private IP addresses exist to save on the limited number of available public IP addresses. There are actually 4 ranges of private addresses: 10.0.0.0 to 10.255.255.255 when you need a lot (16,000,000+) of addresses in your internal network; 172.16.0.0 to 172.31.255.255 when you need up to a million or so; and 192.168.0.0 to 192.168.255.255 or 169.254.0.0 to 169.254.255.255 when you only need up to 254 addresses. These addresses must exist behind a router or gateway, not on the live Internet.
The real genius of these private IPs is that you can get one IP from your ISP (let's say 126.96.36.199), and your router / gateway basically splits that into however many internal (private) addresses you need.