A network portion is the portion of the IP that is not owned or controlled by the host. This includes the broadcast address, which is the portion of the IP that is used for both inbound and outbound transmissions. The host portion of the IP is the portion of the IP that is owned and controlled by the host.
This is the whole point of the IP address, just to make it easy for a newbie to realize what it really looks like, especially if it looks like it’s all linked together from the host.
An interesting point is that when you have a new IP address that has been added to your network, you may find that the host doesn’t know your IP address. So maybe the host knows your IP address, but if the network port is open, it hasn’t seen the IP address, so it may have to use it to try to find out the network port.
Of course, this is just an example of what can happen to a newly added IP address. It has nothing to do with whether or not it was used by a specific person. A new IP address may have been added to the network, but the host may not know it, and so it may be necessary for you to type the IP address into the web browser.
For example, if you have a shared computer with someone else, you could use the same name to identify each person on the network. You may also use a different name if the IP address is unique for a specific person.
The same concept applies to a host. A domain name can also identify the host (like “facebook.com”) and so you may not know what name you are typing into the web browser.
If you think of a domain name as the IP address of a computer in your network, then you can use the IP address in the link. If you think of a web browser as a person on your network that is using a different computer to access the web, then you can use the username and password. However, it is also possible to think of the domain name as the IP address of any computer out there.
Most websites use a domain name like facebook.com or gmail.com to identify their network. A web site can use the domain name to identify itself as a website that is accessible from everywhere (for example, the new web site for the internet is www.facebook.com).
In a sense, the domain name identifies the network and the web site itself. The host part of the IP address tells you that that computer that is using that particular IP address is associated with the domain name. In other words, you can identify an IP address using the host of the computer it is attached to.
This is why you only use the host portion of the address when you do something like log into a computer or access a website using a browser. If you have a connection to a website on your computer, you can use the host portion to identify your computer.