How do I use Vim Folding feature?

Linux.com posted yet another nice article about VIM editor, written by Joe 'Zonker' Brockmeier.

FTA "...The problem with writing and editing on a computer, versus having words on paper, is that it's usually hard to compare text from different sections of a document when they don't fit on the screen together. One way to do it is to use Vim's viewports feature. Another is to "fold" the text. Using Vim's folding features, you can tuck away portions of a file's text so that they're out of sight until you want to work with them again. Here's how..."

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