An "institutional fund" is a type of mutual fund catering primarily to institutional investors, such as pension funds, endowments and other high net worth investors. Institutional funds are characterized by low fees but high minimum investment requirements.
The term "broad based index" usually refers to a stock or bond index designed to reflect the movement some signficant portion of the stock or bond markets. Examples of stock indexes include the Dow Jones Industrial Average (representing 30 of the largest US traded stocks), the S & P 500 (representing 500 of the largest US traded stocks), the Wilshire 5000 Total Market Index (representing actually over 8,000 US traded stocks), and the Russell 3000 Index.