barelist.rb

def this_method_takes_three_arguments(a, b, c)
  # do stuff with three arguments
end

# Now imagine you had an array that contained the three arguments that 
# you wanted to pass into the above method:

arguments = ['foo', 'bar', 'baz']

# You could pass them in like this:
this_method_takes_three_arguments(arguments[0], arguments[1], arguments[2])

# But this will work just as well:
this_method_takes_three_arguments(*arguments)

# This works the other way around as well. If you have a method that is defined like this:
def this_method_takes_a_variable_number_of_arguments(*args)
  args.each do |a|
    # do stuff with the argument
  end
end

# You can then call it with however many arguments you want:
this_method_takes_a_variable_number_of_arguments('foo', 'bar', 'baz', 'monkey', 'banana', 'pineapple', 'whatever')