:a_symbol

There is only one representation of a given symbol in memory, so it really means "the thing named :a_symbol" to the ruby interpreter.

"apple"  # transient and mutable
:apple   # permanent and immutable

Hardcore Rubyists prefer symbols over hardcoded globals or strings. They're very lightweight.

They also look better in code and are easier to type (by one character).

In Alex's Humble Opinion

• Symbols are silly
  • or, symbols are a good experiment with a negative result
• Symbols' main function is to confuse people about hash keys
  • the existence of HashWithIndifferentAccess is an argument against the existence of symbols
  • if you use JSON or Rails, you must code defensively
• Proposal:
  • keep the symbol syntax
  • symbols become immutable strings
  • :foo == "foo".freeze
• See Why are symbols not frozen strings? on StackOverflow