Help me to understand dnx command in docker container entrypoint

I am using asp.net core plus docker container. Based on the https://docs.docker.com/engine/reference/builder/#entrypoint

One of the ENTRYPOINT form is 

ENTRYPOINT ["executable", "param1", "param2"]

So from this http://docs.asp.net/en/latest/getting-started/installing-on-linux.html#using-docker example. The ENTRYPOINT is

ENTRYPOINT ["dnx","-p","project.json", "web"]

So here "dnx" is mapping to "executable" part in ENTRYPOINT. I have two questions here.

1. "-p" is "param1" in ENTRYPOINT, but I don't know what it is for? Because in https://github.com/aspnet/Home/wiki/DNX-utility there is no such a "-p" parameter.
2. I don't know what is the format for the param in ENTRYPOINT. I thought that is string, however in the above example, "param2" here "project.json" is a file in asp.net project. And "param3" here "web" is the custom command in DNX Utility. They are all not strings. So what is the rule for params?

Thanks.