Ahrefs is an SEO tool (Search Engine Optimization) that businesses, agencies, and individuals (who have a website/blog) use to help them understand where they are ranking organically on search engines (primarily on Google).
They essentially scan search engines to see where they are ranking your site as a whole, along with all the pages on your site, at the deepest keyword level.
It even estimates the traffic value of the various pages on your site, by looking at what people are paying Google for in ads on the keywords that your various pages you're ranking for.
This is incredibly useful when you're trying to figure out what a page might be worth to sponsors and advertisers when you eventually look to monetize your site, or are evaluating the value and impact of SEO as compared to other paid marketing channels (critical for businesses and startups especially).

