Docusaurus is a static-site-generator (also called Jamstack).
It builds your site as simple static HTML, JavaScript and CSS files.
Build your site
Build your site for production:
npm run build
The static files are generated in the build folder.
Deploy your site
Test your production build locally:
npm run serve
The build folder is now served at http://localhost:3000/.
You can now deploy the build folder almost anywhere easily, for free or very small cost (read the Deployment Guide).