As Jon would say, ProTip:
Ruby uses the first character of the name to help it determine it’s intended use.
Local Variables
These should be a lowercase letter followed by other characters, naming convention states that it is better to use underscores rather than camelBack for multiple word names
eg. mileage, variable_xyz
Instance Variables
Instance variables are defined using the single "at" sign (@) followed by a name. It is suggested that a lowercase letter should be used after the @
eg. @colour
Instance Methods
Method names should start with a lowercase letter, and may be followed by digits, underscores, and letters
eg. paint, close_the_door
Class Variables
Class variable names start with a double "at" sign (@@) and may be followed by digits, underscores, and letters
eg. @@colour
Constant
Constant names start with an uppercase letter followed by other characters. Constant objects are by convention named using all uppercase letters and underscores between words,
eg. THIS_IS_A_CONSTANT
Class and Module
Class and module names starts with an uppercase letter, by convention they are named using MixedCase,
eg. module Encryption, class MixedCase
Global Variables
Starts with a dollar ($) sign followed by other characters
eg. $global