They are the variables yielded to the block.
def this_method_takes_a_block
yield(5)
end
this_method_takes_a_block do |num|
puts num
end
Which outputs “5”. A more arcane example:
def this_silly_method_too(num)
yield(num + 5)
end
this_silly_method_too(3) do |wtf|
puts wtf + 1
end
The output is “9”.