What does $message and $$message mean?

[Clydebrown]

I would like to know the difference between $message and $$message. I am not getting it properly. Hence, explain it with example.

 

[Vyom]

Here is your difference:
difference between $message and $$message

 

[a_k_s_h_a_y]

This does not help!

Here is your difference:
difference between $message and $$message