The terms overlap, but the campaign goals are different
Sponsored content, guest posts and digital PR can all result in content appearing on another publication, but they are not interchangeable.
Sponsored content
Sponsored content is a paid commercial placement. The brand and publisher agree on the format, price and requirements. The relationship should be disclosed appropriately. Success is usually measured through delivery, audience exposure, referral activity, engagement and business outcomes.
Guest posts
A guest post is a contributed article from an external author or company. Some publications accept guest contributions editorially, some offer them commercially, and others do both under different rules. When payment is involved, the commercial relationship and link treatment should be handled transparently.
Digital PR
Digital PR focuses on newsworthy stories, expert commentary, original data, launches, research or other material that can earn media attention. Some digital PR opportunities are editorial, some are sponsored, and some campaigns combine both.
Which should you choose?
Use sponsored content when you need a predictable commercial placement.
Use a guest contribution when the publication accepts useful contributed expertise and the format fits your message.
Use digital PR when the story itself is strong enough to be pitched as news, research or expert insight.
Do not choose based on a promised ranking
A placement should make sense for the audience and campaign. Search visibility can be a downstream benefit, but no legitimate provider controls Google rankings.