Google overcame Yahoo and Altavista with the ranking algorithms that consider backlinks to your website.
You see blue or other color links everywhere online.
These links lead users to provide more information that is hard to explain in one piece of content.
There are two types of links: internal and external.
Internal links show other pages on your website and external links show other websites.
Links have tags: follow, nofollow, sponsored, UGC, etc.
These tags help search systems consider links in their algorithms.
Links are not created equal.
They have some weight considering the authority of pages and relevance.
There are two ways of earning links: Black Hat and White Hat.
I recommend using a white hat that is harder but the risk of getting filters and sanctions is absent.