What happens when you launch a D application ?

[Suliman via Digitalmars-d-learn]

On SO[1] I got next answer:

"What happens when you launch a D application ? The entry point 
is a C main inside the runtime, which initialize it (the 
runtime), including module constructor, run the unittest (if 
you've compiled with -unittest), then call your main (which name 
is "_Dmain" - useful to know if you want to set a breakpoint with 
GDB). When Vibe.d's main is called, it parses command line 
argument, an optional config file, and finally, starts the event 
loop. Any code that wish to run once the event loop has started 
should use runTask and similar, or createTimer. They should not 
call the code directly from the static constructor (it's actually 
one of the most common mistake when starting with Vibe.d)."

Could you explain what mean "C main inside the runtime". I 
thought that is only one main is possible. And why it's named 
"*С* main" D is not C-translated language.

Same question is about _Dmain -- what is it?

If I will call this() before main? What it will be? Will it run 
before main?

[1] 
http://stackoverflow.com/questions/30302161/cant-connect-to-mysql-mariadb-database-from-vibed-app