difference betweeen 24 and 24 24

1	-$ variable is normal variable 
2
3	-$$ variable is reference variable. 
4
5Ex: 
6
7<?php   
8
9$x = 'kinjal'; 
10
11$$x = 20; 
12
13echo $x;	//kinjal 
14
15echo $$x;	//20 
16
17echo $kinjal;	//20 
18
19?>