Kavach in Hinduism is a protective shield created through the mantra dedicated to a particular deity in the Hindu pantheon. It is of great importance to many Hindu devotees. A Kavacham is created when a deity is invoked to protect every part of the body of person. Wearing Kavach overcomes evil influences on the perosn through prayers.
The Kavach is more akin to a mantra than to a stotra, prayer, for protection of the limbs is an essential part of the Kavacham.
The mantras and prayers invoked in a Kavach are found in Puranas and Tantra texts. For example Narayana Kavacham is from Srimad Bhagavata Purana (6.70).
Recitation of the kavach itself is the spell of protection.
A Kavacham generally mentions every limb of the body specifically and requests the specific deity to protect that particular limb.
In addition to that, negative forces are also mentioned and the deity is solicited to ward off these. Reciting the Kavacha Mantra, touching the respective limbs of the body mentioned therein, is itself the verbal protective spell.
Most of the ancient Kavach are in Sanskrit. There are some Kavacham in Tamil.
An example of a Kavach:
Surya Kavach of Sage Yajnavalkya
May Bhaskara protect my head and the god of extreme splendor my forehead
May the gem of the day protect my tow eyes and the god of the day protect my two ears
May the hot-rayed god protect my nostrils and my mouth the carrier of the Vedas.
May the giver of prestige protect my tongue and the dear god of the people my chest
May the twelve-faceted god protect my feet and the god of all my entire body.
The Kavacham in Tamil belong to a later period and were composed by saints and devotees. Vinayaka Kavacham is from Vinayaka Purana, in Tamil ascribed to Sage Kacciappar and contains nine verses.
Kandar Sashti Kavacham in Tamil is by Devaraya Swamigal and is on Skanda of Tiruchendur. Some Tamil Kavachams are translations of original Sanskrit.
There are about a hundred Kavach. Some are addressed to the Navagrahas and some to the deities of certain temples. All the important gods and goddesses have a Kavach dedicated to them.
Bibliography
Puranic Encyclopedia (1975) By Vettam Mani – Motilal Banarsidass New Delhi
Encyclopedia of Hinduism Volume VI page 22 -IHRF