Rank Math is an SEO plugin for WordPress, made by the company Rank Math. SEO (search engine optimization) means shaping a site's pages and their metadata so that search engines index them and show them higher in results. A WordPress plugin is an add-on that installs into the WordPress site software.
In the WordPress editor, both Gutenberg and Classic, Rank Math shows suggestions next to each post, gives it an SEO score and previews how it will look in search results and on social media. It controls which pages are indexable and adds structured data (Schema markup, a machine-readable description of the page content) in more than 20 types, which can earn rich snippets in Google. It creates sitemaps that update automatically, runs an SEO analysis against 30 factors, and shows keyword performance from its built-in Google Search Console integration. More than 15 modules can be turned on or off.
The core plugin is free to download. Rank Math PRO is a paid subscription, billed annually, that is installed on top of the free plugin; its plans differ by the number of websites and tracked keywords.