Variables starting with ":"

Hi guys,

I’ve been looking for information about this for a while on some ruby
books, and tutorials, but could never find anything.

What’s the diference between regular variables defined as, lets say
“example”, and the ones defined as “:example” ? If there’s a difference,
when should each case be used?

In many examples, it’s common to see code that uses variables with the
:, specially when defining arrays (like cookies[:user_id] = “abc”)…

I’m sorry for the simple/stupid question… I’ve been studying about ruby
only for the last week or so.

Thanks a lot!!