Explain the difference between $var and $$var?

Explain the difference between $var and $$var?

$var is a variable and $$var is a variable of another variable. For example

$var = “Shafin”;
$you= “Anwar”;

echo $var //Output:- Shafin
echo $$var  //output :-Anwar

$$var allows the developer to change the name of the variable dynamically.