Specification :-
Perlite is one of the best growing mediums around.  Used by itself or as a mixture with other mediums.  Perlite is commonly used with vermiculite ( a 50 - 50 mix is a very popular medium), and is also one of the major ingredients of soiless mix's. 

Advantages :-
  1. Improves aeration and drainage of the soil mixture. 
  2. Store moisture and nutrients for plants. 
  3. Is inorganic and does not deteriorate. 
  4. Has essentially neutral pH of 6.5 to 7.5. 
  5. Serves as an insulator to reduce extreme soil temperature fluctuations. 
  6. Is sterile and free of weeds and disease.
Drawback :- 
  1. Doesn't retain water well which means that it will dry out quickly between waterings.  
  2. The dust from perlite is bad for your health so you should wear a dust mask when handling it.