next/head and next/document are both components in the Next.js framework, but they serve different purposes.

next/head is a built-in component that allows you to modify the HTML head tag of your page. You can use it to add meta tags, title tags, link tags, and other elements to the head section of your page. This component is often used to improve the SEO of your website or to add custom styles and scripts to your page.

next/document is a special component in Next.js that allows you to customize the entire HTML document that is rendered for your pages. It is used to provide custom configurations for the HTML body tag, html tag, and other document-level elements. This component is typically used to add third-party scripts or to modify the basic structure of the page.

In summary, next/head is used to modify the contents of the head tag of a page, while next/document is used to customize the entire HTML document that is rendered for your pages.