When other bloggers or site owners link back to a webpage on their own, this is called a “natural link.” For instance, someone writing a blog post about the top 10 credit cards might naturally link to MasterCard, American Express, or Visa.
Link insertions, on the other hand, don’t happen spontaneously; they are done on purpose, and you have to reach out to the website owner. If everything is done correctly, the search engine will regard the inserted links as natural.