Double bracket pointer syntax

I have a C++ program that initializes variables in a struct.

typedef struct
{
        LONGLONG    llSeekPos;
        BOOL        bSeekActive;
    
} WavPLAYBACK; 

I am confused of the double bracket syntax (WavPLAYBACK*) what does that do?

WavPLAYBACK     *pPlayBack;
pPlayBack = (WavPLAYBACK*)pParam;