Are natural links voluntary links?
 

I want to know that
Are natural links called voluntary links if yes then how?
Somewhere else i had read the natural links are reciprocal links.
Which statement is correct and how if any of them is not correct then let me know what does mean actually?

There are cases when someone gets some info from you and by letting the source of the article in naturally become a link.

There are cases when someone gets some info from you and by letting the source of the article in naturally become a link