ActiveJob's default behavior when an exception is raised during execution

I am confused about how ActiveJob handles retries when there is an exception raised during the execution of a job. The Rails Guide about ActiveJob has this example:

10.1 Retrying or Discarding failed jobs

It's also possible to retry or discard a job if an exception is raised during execution. For example:

class RemoteServiceJob < ApplicationJob
  retry_on CustomAppException # defaults to 3s wait, 5 attempts

  discard_on ActiveJob::DeserializationError

  def perform(*args)
    # Might raise CustomAppException or ActiveJob::DeserializationError
  end
end

To get more details see the API Documentation for ActiveJob::Exceptions.

That means there is a method to explicitly tell ActiveJob to retry a job on certain exceptions and at the same time, there is a method to explicitly tell ActiveJob to discard a job on certain exceptions.

But how does ActiveJob handle exceptions when the developer didn't define retry_on or discard_on? What is the default behavior? Would it discard the job? Would it retry the job? And if, how often and in what interval?