Some basics on Mutual Funds?

Hi,
I want to invest in Mutual Funds(in India) for some short period.
Before this I want to have some basic knowledge on MF.
1. What type of Mutual Investments are there?
2. What should be the minimum period one should keep money invested in Mutual Funds?
3. How to purchase Mutual Funds in India?
4. Any Website links to understand Mutual Funds better.

Please help me out to understand above mentioned points.

Regards,
Nitin Rastogi