The only thing I'll add by way of a simplistic explanation as to what IA is is this: it's also about how information is organised on your website, not just how you get to it.
The point of this article is to help people handle their own IA, and this is definitely possible. I personally don't believe basic IA is rocket surgery, anyone can understand it - there's no highfalutin technology concepts involved, or vague terms like 'on the cloud'. Most of it is just common sense, understanding your audience, and adapting your website to accommodate them ← that is the key point. Basic IA is about arranging your navigation and information in a way which best serves your audience.
Navigation design is about organizing information so: 1) people can find it (using their logic, not yours), and 2) successfully disseminating the information you want to get out there.
The 'disseminating information' part may sound peculiar, even contradictory considering I've just said it's about making information easy for users to find. Consider this though; you may be a charity organization and are required to make available certain information to satisfy government regulations. Or, there could be rules about using your website you need to tell people about. With this kind of information, most people (visitors) aren't interested in it, but it still needs to go up somewhere.
Now that the 'disseminating information' portion is out of the way, let's focus on how to 'do IA' on your website. The easiest way I believe is to approach the task by viewing your visitors in terms of customers. This still can be done even if people don't actually buy something from your website (i.e. I'm using the word 'customer' interchangeably with 'visitor').
Once you break down your visitors into different types of customers, you can start designing your menu structure and organizing your text to serve their needs. Some people will only have one 'customer type', whilst others will have four, five or more. The more 'customer types' you have, the trickier it gets to do IA (not impossible though, just more thought is required).
Let's take an online learning centre as an example. A website which offers online courses in areas such as English, mathematics, and so on. If we were to break down the major types of customers they have, we might come out with this: 1) students, 2) teachers.
Students are the ones using the website to access material such as study notes, quizzes, etc. Teachers are the ones that login and create the courses, answer questions from students, run webinars, and so on. Now this is a good starting point, but you may have noticed something. There is actually a sub-division to the concept of a 'student'. And this is very important. You can have a prospective student, someone who isn't a student yet, but would like to become one. This is subtly different to someone who is already a student. And the reason why this is important is because their needs are acutely different. On the one hand, a prospective student is probably going to be interested in what the enrollment fees are. Where-as an enrolled student is going to be interested in accessing online resources.
Identifying and understanding the different customers of your site is the key. Once you know this, you'll make reasoned decisions about what your menu structure should be like. This is why you sometimes see classifieds-style websites with very overt navigation elements like 'For Buyers' and 'For Sellers' ← they know these are users with very distinct needs.
Thinking about your information in terms of satisfying needs (or helping different types of people complete their particular tasks) is what will guide you when designing your menu structure, including what to name pages and where to put text.
