mdns-docker allows you do to, e.g., "ping my-container.docker.local", where it will find the IP of a running container whose name fuzzily matches the host. The way it does it is by running a local mDNS service that listens to `*.docker.local` requests, finding a running container whose name contains the request (here: "my-container"), getting that container's local IP address, and responding to the mDNS query with that IP.
Example: Start a ClickHouse service (as an example) `docker run --rm --name myclicky clickhouse:25.7` and then open `http://myclick.docker.local:8123" to open the built-in dashboard -- no port mapping required!
If you haven't played with mDNS yet, you've been missing a lot of fun. It's easy to use and the possibilities to make your life easier are endless. It's also what Spotify and chromecast use for local device discovery.