The actual provisioning and configuration of the new site collection will be handled via a timer job instead of making it part of the standard workflow. The provisioning process can be a long running job, and there can be stability problems if too many requests are executed simultaneously. The workflow actions were not intended to support long running jobs such as this. By moving the process to a timer job we can take advantage of the robust scheduling mechanism to queue up the requests, and then handle all of the open requests.
Timer jobs have two main components:
The class file that holds the actual execution logic that runs when the timer job is active
The feature receiver is used to handle the initial setup and registration of the job. It will schedule the timer job to run as well as execute any tear down activities that need to happen when the timer job is deactivated