According to the EntryPoint documentation:
EntryPoints are part of the static configuration. They can be defined by using a file (YAML or TOML) or CLI arguments.
Following the link to static configuration, the options for configuration are:
- In a configuration file
- In the command-line arguments
- As environment variables
However, when you look at the Docker Quick Start, no EntryPoints are defined in any of those options, yet you can access both the API/dashboard and the whoami service. Where are the EntryPoints coming from for both services?
Sorry for the newbie question!
After reading a ton more about Docker and how Traefik interacts with it, including this bit:
Traefik creates, for each container, a corresponding service and router.
The Service automatically gets a server per instance of the container, and the router automatically gets a rule defined by defaultRule (if no rule for it was defined in labels).
I'm starting to understand a bit better. I feel like some of this documentation has very important info spread across different places 
By default, Traefik will have an entrypoint called http listening on port 80.
Some options can add more entrypoint. For example, adding the api.insecure configuration will add another entrypoint called traefik and listening on port 8080.