The Purusha is defined in verses 2 to 5 of the sukta. He is described as a being who pervades everything conscious and unconscious universally. He is poetically depicted as a being with thousand heads, eyes and legs, enveloping the earth from all sides and transcending it by ten fingers length - or transcending in all 10 directions. All manifestation, in past present and future, is held to be the Purusha alone. It is also proclaimed that he transcends his creation. The immanence of the Purusha in manifestation and yet his transcendence of it is similar to the viewpoint held by panentheists. Finally, his glory is held to be even greater than the portrayal in this sukta.
The Purusha Sukta is a most commonly used Vedic Sanskrit hymn. It is recited in almost all Vedic rituals and ceremonies. It is often used during the worship of the Deity of Vishnu or Narayana in the temple, installation and fire ceremonies, or during the daily recitation of Sanskrit literature or for one's meditation.
The Purusha Sukta is an important part of the Rig-veda (10.7.90.1-16). It also appears in the Taittiriya Aranyaka (3.12,13), the Vajasaneyi Samhita (31.1-6), the Sama-veda Samhita (6.4), and the Atharva-veda Samhita (19.6). An explanation of parts of it can also be found in the Shatapatha Brahman, the Taittiriya Brahmana, and the Shvetashvatara Upanishad. The Mudgalopanishad gives a nice summary of the entire Purusha Sukta. The contents of the Sukta have also been reflected and elaborated in the Bhagavata Purana (2.5.35 to 2.6.1-29) and in the Mahabharata (Mokshadharma Parva 351 and 352).
The most commonly used portion of the Sukta contains 24 mantras or stanzas. The first 18 mantras are designated as the Purvanarayana, and the rest as the Uttaranarayana. Sometimes 6 more mantras are added. This part is called the Vaishnavanuvaka since it has been taken from another well known hymn called the Vishnusukta, a part of the Rig-veda Samhita. Though the mantras of the Uttaranarayana and the Vaishnavanuvaka do not seem to have any coherence with the 16 mantras of the Rig-veda Samhita, tradition has somehow tied them together.
The Purusha Sukta is a rather difficult text to explain in a modern way. This is primarily because of the archaic language that cannot always lend itself to interpretations based on the classical Sanskrit, and that many of the words can be taken in several different ways, both literal and symbolic.
Nonetheless, the Purusha Sukta gives us the essence of the philosophy of Vedanta, the Vedic tradition, as well as the Bhagavad-gita and Bhagavata Purana. It incorporates the principles of meditation (upasana), knowledge (jnana), devotion (bhakti), and rituals and duties (dharma and karma). This is why it is highly regarded and extensively used today as much as thousands of years ago.
In a way, this is a message of love, that the Purusha would consume himself in the fire of creation, to create all the worlds. From this sacrifice did all of creation emanate. This is central to the message of the Purusha Sukta.
vedAhametam purusham mahAntam Aditya varNam tamasaH parastAt | tam evam vidvAn amRta iha bhavati na anyaH panthA vidyate 'yanaaya ||
This great Purusha, brilliant as the sun, who is beyond all darkness, I know him in my heart. Who knows the Purusha thus, attains immortality in this very birth. I know of no other way to salvation.