A dynamic request is a request to a non-static resource that was not served by any cache and, therefore, reaches the origin webserver (Apache). In other words, all requests that are served from a cache, including our own Nginx cache and Cloudflare edge cache, do not count as dynamic request.
All our plans come with a set amount of dynamic requests included. The usage of dynamic requests is measured by counting the number of requests that reach Apache. Dynamic requests will also include all requests that cannot be cached in the first place, like POST requests. Typical examples of POST requests are ajax and API requests. These are mostly generated by your theme or plugins, for example, when sending back tracking data to your site or for updating the information in a shopping cart.
You can read more about Dynamic Requests in our Help Center.