Rendering engines render content and layout data returned by the Sitecore Layout Service from a Sitecore instance.
Within the Sitecore Headless Services module, Sitecore provides two implementations of a rendering engine:
Rendering engines and the ASP.NET Rendering SDK
When working with the ASP.NET Rendering SDK, you must perform some configuration to use the Rendering Engine with your application.
For details, refer to the using the Rendering Engine with the ASP.NET Rendering SDK.
Rendering engines and JSS
To learn more about how to use rendering engines with JSS, refer to Rendering engines and JSS.
If you are using SXA, you can configure a rendering engine in the settings of your Headless tenant with the help of the Server side rendering engine field.