We speak of 3 different types of links which help with SEO:
1. Internal links – from one page from the site to another page of the same site. These links help with faster indexing the site by the crawlers but also transmit the authority between pages. For example, if the main page of the site is important and has many links, adding an internal link on it to a secondary page, you can increase the importance of the latter. With internal links and with the no-follow attribute you can control what the SEO specialists call “internal link juice”.
2. External links – links from your site to other sites. Here it matters, as much as possible, to add links to sites which are relevant for the field of your own site. For example, if you have a site about cars, it is best to add a few links to other important car sites. I will give you a concrete case.
3. Inbound links (IBL) – links which others make to your site. Not only will you receive traffic from the sites where your links are posted, but they will also send you their link juice. The more important the site you receive link from, the more Google will consider your site as being important and will raise it in SERP, will take it out of supplemental index or will completely index it. The form of the IBL is also important on the respective site: you mostly benefit from an increase in SERP if the IBL comes to you with a keyword in the anchor text. So, for the site with the eggs, an IBL will have more value if the link is added as “Colored Eggs” than if it is added as “visit an interesting site HERE”.
IBL’s are the most important and are outside your control (with internal and external you have complete control) so you must obtain them through 3 methods:
1. Link exchange – you ask for a link on another site, at the same time adding a link to them from your site
2. Paid linking – you buy a link on another site
3. Quality content – by writing a quality content, you will receive links to other sites, which will contribute to raising the pages with the respective content and implicitly of your whole site. He quality contents can be virally extended, so it has unlimited potential.