Plex organizes video, music and photos from personal media libraries and streams them to smart TVs, streaming boxes and mobile devices. This container is packaged as a standalone Plex Media Server. The parameters are split into two halves, separated by a colon, the left hand side representing the host and the right the container side. For example with a port -p external:internal - what this shows is the port mapping from internal to external of the container. So -p 8080:80 would expose port 80 from inside the container to be accessible from the host's IP on port 8080 http://192.168.x.x:8080 would show you what's running INSIDE the container on port 80.