Baffled by the registration command -WorkflowHostUri

Afternoon All

Hopefully you can demystify something for me.  After much wailing and gnashing of teeth I've got Workflow Manager installed.  Apparently installing Visual Studio 2015 in your dev environment is not a good idea, so don't do that.

Anyway I've got to the point where I need to register using the following command.

Register-SPWorkflowService -SPSite "http://myserver/mysitecollection" -WorkflowHostUri "http://workflow.example.com:12291" -AllowOAuthHttp

I graps the first part, where the SPSite is the site I wish to enable 2013 workflows, but I am slightly mystified by the -WorkflowHostUri part.  Where do I get that from, or is it something that is created through this process.

I hope that makes sense.

Many thanks

John.