C style struct declaration

I have a quick question about C style struct's. I was digging through some sample code and found a struct declared in the following way:

typedef struct _STRUCTNAME
{
   // struct contents
} STRUCTNAME;

Please note the lack of an underscore on the second time STRUCTNAME shows up. My understanding was that this would declare a single _STRUCTNAME called STRUCTNAME and no more objects of this struct could be instantiated.

However, this does not seem to be the case. A struct of this type was never actually instantiated in the code except in one place: in a global array of such objects that was used in random places:

const struct STRUCTNAME ARRAYNAME[] = 
{
   // various STRUCTNAMEs declared here
};

Note the lack of an underscore again (which I thought was the name of the instantiated object?)

Is my understanding completely off?

Could someone explain?