C++ - What does “Stack automatic” mean?

{
   obj a;
} // a is destroyed here

{
    obj* b = new obj;
}

{
   FILE* pF = fopen( ... );
   // ... do sth with pF
   fclose( pF );
}

{
   std::fstream f( ... );
   // do sth with f
} // here f gets auto magically destroyed and the destructor frees the file

{
   string v( "bob" );
   string k;

   v = k
   // v now contains "bob"
} // v + k are destroyed here, and any memory used by v + k is freed

int main() {
    int a;
    auto int b;
}

auto a = std::max(1.0, 4.0); // `a` now has type double.

MyObject x = MyObject(params); // onto the stack

MyObject * y = new MyObject(params); // onto the heap