Could someone explane me when use Variable Variables?

Question

it is my first steps in PHP and Variable Variables is confuse me, it is a concept that I don't see in other language.
An example would help me.

Answer 1

for example,
if you have a very long variable name that you want to shorten for frequent use in your script, then you could use this technique to save yourself some typing,

in code:
$your_name_is = 'Jorge Daniel Lopez Irusta';
$name = 'your_name_is';
echo $name;