Validates_inclusion_of method dealing with array

Hello,

Im working through the agile book and ran across a line which I dont
understadn how it works exactly.

validates_inclusion_of :pay_type, :in => PAYMENT_TYPES.map {|disp,
value| value }

Could someone please explain what this part does: {|disp, value| value }

Is it only looking at the second value in the array?

Thanks in advance!