The following tutorial will show you how to redirect your WordPress site's domain from non-www to www or vice versa. Redirecting one to the other is useful for SEO.
If you go to https://www.wordpress.org, you'll see the URL changes a bit once you click enter. It goes to the non-www version. In order words, it goes to https://wordpress.org. It's a subtle change and it's usually not noticed by users.
So why have they done this? It's because, technically, the two are different domains but they have the same content. Without the redirect, they end up with duplicate content. With the redirect, they only have one site, so only one set of content.
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