The Samhitas are collections of Vedic hymns. The Brahmanas are treatises written in prose, dealing with the conduct of sacrifices and other rites associated with them. The Upanisads deal with philosophical truths and esoteric wisdom.
The Aranyakas form a link between the ritualism of the Brahmanas as and the philosophy of the Upanisads.
The extant Aranyakas of the four Vedas may be listed as follows:
Aitareya Aranyaka, Sankhyana Aranyaka (sometimes called Kausitaki Aranyaka also).
Brhadaranyaka (the earlier part of the Satapatha Brahmana, the later part being the Upanisad).
Taittiriya Aranyaka, Maitrayaniya Aranyaka.
Last part of the Tandya-mahabrahmana(also known as Pancavimsabrahmana), Talavakara Aranyaka.
No Aranyaka is available.