1. A public charitable or religious institution can be formed either as a Trust or as a Society. It generally takes the form of a trust when it is formed primarily by one or more persons. To form a Society at least seven persons are required. Institutions engaged in promotion of art, culture, commerce etc. are often registered as non-profit companies. You can form and register the trust as per the Indian Trusts Act by executing a trust deed.
2. Under the Income Tax Act, wholly charitable and religious trusts are exempt from tax. A notified approval from the DG Income Tax Exemptions may be obtained under Section 10 (23C), subject to the fulfilment of certain specified conditions.