Don't worry if you can't pronounce Canonicalization. Most people just refer to it as dub-dub-dub vs. Non-dub-dub-dub. It is important that one or the other be chosen and used consistently. One should redirect to the other (which WordPress now handles on its own). But just to make sure everyone is clear, it simply prevents search engine bots (especially Google) from sending some of that all-important link juice you receive from backlinks to one url and some of it to another. If both are in play, then you end up with multiple copies of the same page, i.e. duplicate content. (www and non-www). If Google understands that both versions are the same, all that link juice gets consolidated and you get the full impact from it. It only takes a second to handle, but the impact can be great.