These are different types of resource hints that browsers use to optimize the loading of resources. Here's what each one does:

1. preload: This directive is used to tell the browser to start loading a resource early, before it's needed. This is useful for resources that are discovered late in the loading process but are needed early, like a font used in CSS.
   
   

   <link rel="preload" href="style.css" as="style">

2. prefetch: This directive is used to tell the browser to load a resource during idle time, in anticipation that it will be needed in the future. This is useful for resources that will be needed on subsequent navigations/pages, like a JavaScript file for the next page.
   
   

   <linkrel="prefetch"href="page-2.js">

3. dns-prefetch: This directive is used to tell the browser to resolve the DNS of a specific domain before it's needed. This is useful when your page references resources hosted on other domains.
   
   

   <linkrel="dns-prefetch"href="//example.com">

4. modulepreload: This directive is similar to preload, but it's specifically for loading JavaScript modules. It tells the browser to fetch a module script and all its dependencies ahead of time.
   
   

   <link rel="modulepreload" href="module.js">

5. preconnect: This hint tells the browser to establish a connection to a specific domain, including DNS resolution, TCP handshake, and optional TLS negotiation. This is useful when your page will soon make a request to a third-party domain, and you want to ensure the connection is ready when needed.
   

   <link rel="preconnect" href="https://example.com">

6. prerender: This hint tells the browser to fetch and render a whole page in the background. However, it's not widely supported and can consume a lot of resources, so it's not commonly used.
   

   <link rel="prerender" href="page-2.html">

There are a few more such as

1. Preconnect-src: The preconnect-src is a Content Security Policy (CSP) directive that allows web developers to specify a list of origins that the browser should preconnect to, establishing early connections for improved performance.
2. Prefetch-src: The prefetch-src is a CSP directive that allows web developers to specify a list of origins from which the browser can prefetch resources, potentially improving the performance of future navigations to pages that use those resources.
3. Preload-src: The preload-src is a CSP directive that allows web developers to specify a list of origins from which the browser can preload resources, ensuring they are available as soon as possible.

In all cases, these directives help the browser prioritize resource loading more efficiently, which can lead to performance improvements in your web application. these hints should be used judiciously, as each one consumes resources. It's best to measure and understand the performance impact of each hint before using it.