can't understand symbols !! could anyone explain please ?

Question

Symbols

In the previous example we used strings as keys for the hash, but Ruby has a more elegant and faster way for creating and accessing hash indexes than using strings.
Symbols are similar to strings, but they are immutable, meaning that they cannot be changed.
A symbol is created using a colon and a name, for example:
a = :id

In the code above :id is a symbol. You can also think of :id as meaning the name of the variable id, and plain id as meaning the value of the variable.

Answer 1

Reading this article was useful to me:http://rubylearning.com/blog/2007/11/26/akitaonrails-on-ruby-symbols/

Answer 2

you can use symbols instead of strings if you want to make you code run faster. They are simliar to strings, but they just can't be changed.

Answer 3

Using symbols :id saves memory, because they are only stored once.

Answer 4

Look at the code:
arr = { "name" => "John" }
arr = { :name => "John" }
arr = { name: "John" }

All of them doing same task.
Which do you think is short?