In ruby curly braces have different meanings:

1. A hash:

my_hash = {:a => 1, :b => 2}

or the same but more JSON like syntax ( ruby >= 1.9 only)

my_hash = {a:1, b:2}

same as:

my_hash = Hash.new
my_hash[:a] = 1
my_hash[:b] = 2

2. A block:

in rough and short: a block is a piece of code which will/can be executed either ‘later in time’ or ‘in a different context’

3.times do
 puts "HI"
end

or

3.times {
 puts "HI"
}

especially in one line it reads nice:

3.times { puts "HI" }

usually blocks have parameters which allows them easily to be identified:

  3.times { |index| puts "Loop: #{index}" }

oh and here’s a third case:

3. curly braces us variable within a string_

name = "Heinz"
puts "#{name} Ketchup is toll"

same as

name = "Heinz"
puts name + " Ketchup is toll"

I hope this helps to understand. I have to admit, curley braces have lots of different meanings in ruby and are indeed confusing - quite often they are ‘shortcuts’ to make your code read nice.