You can find out what services are registered with the container using the console. To show all services (public and private) and their PHP classes, run:
$ php bin/console debug:container
# add this option to display "hidden services" too (those whose ID starts with a dot)
$ php bin/console debug:container --show-hidden
To see a list of all of the available types that can be used for autowiring, run:
$ php bin/console debug:autowiring
You can get more detailed information about a particular service by specifying its id:
$ php bin/console debug:container App\Service\Mailer
# to show the service arguments:
$ php bin/console debug:container App\Service\Mailer --show-arguments