Running your SEO audit you find that there are many spammy sources linking back to your website, you’ll want to disavow these links. Disavowing is a process that lets Google know that you no longer want to be associated with those links, and if you don’t disavow the backlinks then your SEO will suffer because Google sees your site as associated with those spammy sites. You want to first try and get the websites to remove your backlinks on your own by talking with editors, but if you have no luck, disavowing is your best option.