What is the area between the taxiway and runway shown in the picture below?
Additional information on the airport would have been nice, but from the markings it looks like it simply is a pad where two aircraft can be positioned at once. 

This can be useful where you have a case of eg. one aircraft needing additional time to be ready for take-off while the aircraft behind is all set, or a larger aircraft in front being held back to allow a smaller aircraft to pass it and take off first. 

Copenhagen Airport (CPH) has a similar layout at the end of one of the runways, as shown below, although this is using two taxiway stubs rather than one solid pad.