Requirements for Travel to India
If you plan on travelling to India, you will need to acquire a tourist Visa. Tourist Visas are issued to people who want to come to India to visit friends and go sightseeing. Although tourist Visas can be granted for more than six months, depending on the applicant's nationality, it's not possible to remain in India for longer than six months at a time on a tourist Visa.
Additionally, if you wish to explore business opportunities or conduct business in India, you must acquire a business Visa. Business Visa applicants will require a letter from the organization that they intend to do business with, stating the nature of the business, duration of stay, places to be visited, and intention to meet expenses. Business Visas are valid for six months or more, with multiple entries.
However, holders usually aren't allowed to remain in India for more than six months at a time (depending on the nature of the business). Ten year business Visas can be granted to foreigners who set up joint ventures in India. This type of visa differs from an employment Visa in that the applicant won't be working for, and earning an income from an organization in India.
Link(s):
http://goindia.about.com/od/visas/tp/Guide-To-Indian-Visa-Types.htm