What is the difference between CMD and ENTRYPOINT in a Dockerfile

Question

CMD and ENTRYPOINT are two commands in Dockerfiles that look identical to me. But I assume there is a (minor?) difference between them; otherwise, having two instructions for the same thing would be redundant.

The CMD documentation

The main purpose of a CMD is to provide defaults for an executing container.

The ENTRYPOINT documentation

An ENTRYPOINT helps you to configure a container that you can run as an executable.

So, what's the difference between the two then?