Backlinks refer to hyperlinks on one website pointing to another website. Search engines regard them as indicators that your website has valuable content because the link implies the endorsement of another website.

Those pages that have high-quality backlinks can rank higher on search engine results pages.
What makes for high-quality backlinks?
Trust is a big factor in a backlink helping you. If a website that Google considers having a sterling reputation links to your website, that’s a significant vote of confidence. For example, if your small rural news website had a story about sustainable energy picked up and linked to by ABC News or the BBC, Google would assume that your website had value as a news website and thus would rank your pages higher on search results.
If you have websites that Google considers “spammy” linking to your website, it won’t help you and will likely harm your SEO rankings.
What makes for low-quality backlinks?
Google is in the pleasing their searchers business. They rely on the “PageRank” algorithm as one of the key signals of the websites or web pages most likely to be relevant to their users. Because it’s so well known, spammers then try to use to it to their advantage to fool the system. And so, Google is always fighting “linkspam” which are links between pages that are there for reasons other than merit.
If this has occurred either intentionally or not, you may get a message from Google informing you that your website is in violation of their quality guidelines. At that point, you’ll need to get rid of or “disavow” as many low-quality or “spammy” links to your website as possible. Otherwise, you will get penalized in the form of lower and lower search rankings.
It is possible to organically receive a link from a spammy website that are just lists of products and links with no substantive content. That link probably was placed by a robot, and it is not helping your website, so those are safe to remove.
Negative SEO Attacks
And then there are the bad backlinks that are a part of an attack strategy called “Negative SEO Attack.” Your competitor can purchase backlinks and point them at your domain until you get penalized and your SEO drops through the floor.
The victim of a Negative SEO Attack must disavow (with extreme prejudice) all of those attack links that targeted their website.
In general, you should only disavow a link that you know for sure is bringing you down. Not every link from a low-traffic or low-domain authority website is a bad link. It probably won’t hurt or help much. But for the obnoxious ones and the “bad” ones, you must counter-attack.
Disavowing a Backlink
The goal of disavowing a backlink is to get Google to ignore those links. If the link disavow is successful, it won’t be used for or against you when Google determines your ranking in the search results. It’s certainly in their best interest to honor your request but they are not obligated to.
How to Disavow Backlinks
The Google Disavow Tool allows you to: Define the links you choose to disavow, create that list, and then upload that list to the tool. It’s simple except for that obvious “rub” of identifying the bad links. You might be surprised to learn that even a small website can accumulate thousands of backlinks over time. You’ll ideally use the Google Disavow Tool in conjunction with other tools such as Semrush, so you can make sure you combine all link sources and maximize your disavow opportunities.
Links to Keep
This is simple. You want links that have the potential to send you referral traffic, friendly faces, and potential business. You want links that align topically with your website’s content, and you want those that come from known (ideally) and trusted (certainly) sources.
Conclusion
Disavowing links is just one part of maintaining SEO health for your website. It’s wise to have an occasional SEO audit to fully suss out where you can improve and what may be holding you back from reaching the desired heights of page-one search results.
Such an audit digs deeper into the Google algorithm to seek to satisfy their requirements for loading time, mobile optimization, broken links, bounce rates, and many more. The algorithm is always changing and thus the “rules” for who Google decides to reward and punish are changing as well. And this is a game that you really need to win.