Ruby Symbols are names that follow a : character. They're a quick way of getting at data, where (for example) you have a fixed key or name in a hash, and you'll find them commonly used in many definitions such as in Ruby on Rails. I've put a short example [here]
(written 2010-02-02)

 R107 - Collections (Arrays and Hashes) in Ruby
  [3435] Sorta sorting a hash, and what if an exception is NOT thrown - Ruby - (2011-09-12)
  [3257] All possible combinations from a list (Python) or array (Ruby) - (2011-04-23)
  [3255] Process every member of an array, and sort an array - Ruby - (2011-04-21)
  [3253] Is this number between? Does this list include? - Ruby - (2011-04-18)
  [2976] Creating, extending, traversing and combining Ruby arrays - (2010-09-30)
  [2621] Ruby collections and strings - some new examples - (2010-02-03)
  [2606] Sorting arrays and hashes in Ruby - (2010-01-30)
  [2291] Collection objects (array and hash) in Ruby - (2009-07-16)
  [991] Adding a member to a Hash in Ruby - (2006-12-16)

Back to Comparing floating point numbers - a word of caution and a solution

Previous and next or Horse's mouth home

Forward to Passing code to procedures and yield in Ruby

Handling unusual and error conditions - exceptions
Direct access to object variable (attributes) in Ruby
Passing code to procedures and yield in Ruby
What are Ruby Symbols?
Comparing floating point numbers - a word of caution and a solution
Defining a static method - Java, Python and Ruby
String to number conversion with error trapping in Ruby
Neatly formatting results into a table
Constants in Ruby