What you are looking at is the strings of 100 warm white LED lights that connect to one of the two adapters
You can add up to 10 of these strings of 100 lights to the adapter to create a string anywhere from 100 to 1000 lights. Each string of 100 lights is 10m long which is an easy length to wind through your Christmas tree.
If you want to use the lights through a garland or use them as a single length (ie. anywhere from 10-100 metres of cord running end to end off one transformer) then you need the straight line adapter.
Check out the video to see how easy it is to string these 10 metre lengths of lights through your tree. (Note, in the video we use the old style 5 finger adaptor - now you can have up to 10 strings running from the one transformer.