The larger context in which this fits is: You have a body of information you wish to publish. In publishing that information you can organize it any way you want. Your goal is likely to gain readership who is interested in the body of information you have to present. The question is, how do you reach those readers?
You first have to understand what keywords is being used by the readership you're interested in.
It's about finding the presentation for your material that makes it interesting to your potential readers. If you present what they're looking for, they'll have a better chance of finding you, and have a better chance of grokking what you're saying. And, it seems, this is largely based on the "key word" phrases you use. This is true at least in helping your potential readers find you in the first place, because it's very likely they're going to a search engine to find you. Search engines rank based on what keywords in the users query match keywords in the universe of pages indexed by the search engine.
Let's consider a practical case, let's talk about digital cameras. Someone looking for a digital camera might be looking for reviews for a specific model. So their query might be "Nikon coolpix s4 review" or whatever specific camera they're looking for (BTW, I just bought a Coolpix s4, and it's really nice). You have two choices .. one is to make pages that aren't clearly associated with specific cameras, e.g. a list of all Nikon digital cameras. Or you might target the page to "the latest in Nikon digital cameras". But if you do that will it rank highly for the "Nikon coolpix s4 review" search? No.
If, instead, you make a page optimized for the "Nikon coolpix s4 review" search, it will tend to reach the people making that search.
The article I linked at the beginning of this posting goes into this in more depth. Good luck in finding your audience.