This is the genuine army issue poncho liner, also known as a woobie blanket. They are water resistant and used for extra warmth in the rain. You can use the liner’s strings to tie this blanket to your poncho. Also, you can use the blanket as a sleeping bag in warmer climates.
This is not the actual poncho, this is literally just the blanket that can be used as a liner inside the poncho, there is no hole for your head in the liner.