Build it, and they will come. And if it's good enough, they'll share it with other people by linking to it. This category includes any content created and published specifically to attract links. The various forms of linkbait cover perhaps the most popular techniques of getting a natural looking link from a wide number of sites that has been used in recent years. To make it extra useful, linkbait can work particularly well for targeting particular keywords - read more in the later points.

Since badges & widgets don't fall under the description of linkbait used above, they can be considered quite distinctly. They exist to give value to the page they are embedded on. Links included within them typically take the form of a 'credit' that doesn't need to be followed by a user to enjoy the widget/badge - but the search engines' algorithms barely notice the difference.