A request for the Docker doc-ers: networking

I’ve been much more hanging out on Stack Overflow than here of late. One thing I’ve been seeing a lot is repeated questions (multiple times a day, with various language/database combinations) that are some variation of the following:

I’m trying to run an application, here is my docker-compose.yml file with my application and the database. When I start it, the application fails saying “failed to connect to database on connection refused”. Why?

It seems like it would be very helpful to the typical beginning Docker user – certainly more useful than the Docker Swarm tutorials – if the “Get started” sequence on the front of docs.docker.com contained a page explaining how standard Docker networking works, when and how to use inter-container DNS, what localhost actually means, and how to use docker run -p. “Connect to a non-Docker database on the same host” is a slightly advanced topic but is also a somewhat regular question.

Is there space for a “really frequently asked questions: networking” on the docs.docker.com front page?