True about Macula Densa is/are:
Function of Macula Densa (Tubulo glomerular feedback): 

Macula densa senses change in NaCl concentration. 
For autoregulation of GFR.
Also known as Tubulo glomerular feedback.
Macula densa senses change in NaCl concentration.
For autoregulation of GFR.
All of the above.