Helping people with computers... one answer at a time.
IntERnet and IntRAnet are two different things. I'll look at just what I think an intRAnet is, and what most people think it is.
What's the difference between an intranet and the internet? At my work we have a page on our website that everyone at work calls the intranet but it's just a hidden page that only staff who have been given the link and login password know how to find, but I don't consider this an intranet (even though I'm not entirely sure what an intranet is defined as). I thought an intranet would be a server that is not accessible to anything outside the network which is definitely not how we have our 'intranet' set up. Anyway, I thought maybe you could shed some light for me and others.
There's no real hard-and-fast definition ... or rather what definitions exist tend to get used and abused to the point of being very, very fuzzy at best.
I'm with you in my general belief of what intranet should mean.
But "should" and "does" are often at odds, especially as usage changes and definitions struggle to keep pace.
First, we need to make a quick distinction between a local or corporate network and "The Internet".
Many companies and other organizations have internal networks - networks on which all the computers and equipment "inside" the company resides, and which cannot be seen or accessed from the outside (at least not without special arrangements of some sort).
This is actually pretty equivalent to you own home network as you sit behind your router. You may have a couple of computers that can share files and perhaps a printer internal to your home, yet inaccessible from "The Internet". Of course from your internal network you can access The Internet just fine, typically through your router.
So, you have a LAN (think of it as your internal, "corporate" network), and from it access to The Internet.
Intranet technically just refers to an internal network, so in a sense you already have one.
What many people use to distinguish an intranet from a run-of-the-mill internal network or LAN is the presence of one or more web servers. It's an artificial distinction, but it's part of that fuzziness I was referring to earlier.
By web server I mean simply that one or more of the machines on your internal network is running the software that allows it to respond to browser based "http:" requests and return pages for the browser to display. Most often that's done by quite literally running the same web server software you'd find on internet servers, but restricting access such that it can be reached only by other computers on your local network.
In fact, there are even some obscure default behaviours built in to much of the software on your machine today. A browser request made of http://machinename where machine name has no dot (".") in it by definition cannot be an internet request - so the software handles it as a request on your local network. Many of the web servers on internal corporate networks are referenced exactly like that: by their machine name.
Those web servers that aren't really on "the web", but rather your internal network, make up what most people think of as an intranet. A set of web sites and servers available only internally, on the internal network.
That's pretty much what you described as your understanding, and deep down, that's exactly what I think of when I think intranet.
But apparently others decided that was too simple.
What companies find is that employees want to access the internal intranet while at home or on the road - via the internet.
There are several common solutions:
Don't support it. Not popular with the traveling or work-at-home crowd, but common.
Use a VPN or Virtual Private Network. Essentially a VPN server is placed on the corporate network that acts as a bridge for incoming connections from the internet. With the appropriate VPN software and login credentials, a remote computer can connect to the corporate network or intranet via a connection over the internet. The computer acts as if it's connected to the internal corporate network, because it is - through the VPN connection. This is actually fairly common since it essentially gives access to all resources on the corporate network, not just the web servers.
Use Remote Desktop. In this network configuration, individuals are allowed to connect directly to a computer on the corporate network and use it as if they were sitting in front of it. The computer they have at home isn't really on the internal network, it's just running a program - the Remote Desktop Client - that opens a window onto the computer back at work that is on the internal network.
Fake an intranet on The Internet. I'm seeing this more and more. Essentially, it operates exactly as you described: a server is placed on the public Internet, and access to it is somehow controlled - typically by login credentials such as a username and password. That server (or servers) is then called the company "intranet" because it serves the same purpose as the prior examples: a server accessible only to authorized company employees. It can be reached from within the company network, since presumably any server on the internet could be, and it can be reached from any employee's computer as well, because it really is on the internet. The only thing preventing public access is the existence of a username/password requirement.
I'm with you, I don't consider that last one an "intranet" at all - it's simply an access controlled set of servers living on the public internet.
But, as so often happens, common usage is outpacing accuracy in such a way as to redefine the term.
So it goes.
Finally, I'll quote the definition from Wikipedia, which sums up most of what I've just said in a more formal way:
An intranet is a private computer network that uses Internet Protocol technologies to securely share any part of an organization's information or network operating system within that organization. The term is used in contrast to internet, a network between organizations, and instead refers to a network within an organization. Sometimes the term refers only to the organization's internal website, but may be a more extensive part of the organization's information technology infrastructure. It may host multiple private websites and constitute an important component and focal point of internal communication and collaboration.
In other words, it's internally networked computers and websites.
Except when it's not.