What are "natural" links

[kadesmith]

With the recent Penguin update, I've seen this term "natural links" thrown around a lot.  How do you build natural links?  That to me seems like an oxymoron. If I'm building them aren't they synthetic in nature as it is?  Can anyone give me a sample of a natural link?

[William.Lau]

You make awesome content.

Another person or person in your niche(best) is interested in that content.

Person republishes and puts your content on their page and links to you as source.

That is natural, not contacting people to buy links. Natural links are best as it shows interest and buzz for your site.

Social media is natural too, similar to word of mouth. Its natural.

[Copstead]

Basically a "Natural Link" is when someone links to your site for any reason without you having to ask them or pay them to link to you.  They found value in your site and wanted to share with others.

It's not a type of link, but how the link was acquired.