What are Symfony services and how do you define them?

Symfony services are objects that perform specific tasks and can be reused throughout your application. They are defined in the service container.

To define a service:

1. Create a PHP class that represents the service.
2. Configure the service in config/services.yaml.
3. Inject dependencies as needed through the service's constructor.

Example service definition:

services:\n    App\Service\MyService:\n        arguments: ['@another_service']