| Client | Client simulates a browser and makes requests to a Kernel object. |
| HttpKernel | HttpKernel notifies events to convert a Request object to a Response one. |
| Kernel | The Kernel is the heart of the Symfony system. |
| KernelEvents | Contains all events thrown in the HttpKernel component |
Interfaces
| HttpKernelInterface | HttpKernelInterface handles a Request to convert it to a Response. |
| KernelInterface | The Kernel is the heart of the Symfony system. |