A guest post is a piece of text you publish on someone else's website, usually with a link back to your own website. Used correctly, it is a legitimate tool – you bring your expertise to an audience that does not know you, and you gain a mention along with a link. The line between legitimate and risky runs through the value of the content and through transparency. If the article is written for the reader, draws on your actual practice, and the link within it makes sense, it is ordinary collaboration. If it involves mass-produced texts placed on websites without an audience, created purely for the link, or a paid placement without disclosure, it is a breach of the rules. When choosing a website, check whether it has genuine traffic and topical relevance. A paid placement should carry the appropriate link disclosure.
See also: Nofollow, sponsored and UGC attributes, Digital PR for AI Visibility, PBN and risky practices.