Workflow Callback URL vs Workflow Trigger URL

Question

I have found there are two "callback" APIs, Workflow - List Callback Url vs Workflow Triggers - List Callback Url . It seems only the latter one could trigger a workflow run with a "manual" HTTP trigger, while the former one just responses with 404. I would like to know in which scenario the former one is used?

Besides, I have found the latter one seems to be appending /trigger/:triggerName/invoke, is this guaranteed or not? If not, is there a way to tell the two callback URLs apart?