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What is Index Fund
An index fund is a a mutual fund which tries to replicate an index of a financial market. (For eg: Sensex or Nifty). An Index fund follows a passive investing strategy called indexing. It builds a portfolio with the same stocks in the same proportions as the index. The fund makes no effort to beat the index. The purpose of the Index Fund is to earn the same return as the index over a period of time.
What is ETF
ETF stands for Exchange Traded Funds — these are funds that trade on the stock exchange just like any stock. And they are stored in yuor Demat Account just like any Shares you purchase.
Why are Index Funds/ETF’s not as popular or not  advertised like other Mutual Funds ?
Expert Professionals / AMC’s don’t make enough fees from them, so they often go ignored. Just like Term insurance….. , Term Insurance is not promoted as much. Insurance companies do not benefit from them (You can see the correlation…., What is good for Investors and also available for cheap, is not often promoted enough. Because it does not pocket enough profits for the providers/agents…….)
What is the basic difference between Index Funds/ ETF’s  and Mutual Funds?
Mutual Funds try to beat the index over a period of time. This is active investing. Fund Managers are paid to beat the index over a period of time by generating alpha (The excess return of the fund relative to the return of the benchmark index is a fund’s alpha.).
Index Funds/ ETF’s on the other hand, try to mirror the index returns. This is known as passive investing.
What is the advantage of Index Funds/ ETF’s over Mutual Funds?
– Much Lower Expense Ratios (AMC’s are much lower)
– More Flexible
– Transparent
– Approximately 60%-80% of equity mutual funds underperform the average return of the stock market over a period of time. This is the price of “active management”.
– On top of this the AMC charges 2-2.5% of the portfolio value annually.
So , you have to pick the funds carefully. This becomes just like picking Individual Stocks. Of course, if you pick up the right funds (or for that matter right stocks) , then you would be beating the Index handsomely. However this process requires good amount of time, effort and judgement on your part. It sounds simple but is not easy.
– On the other hand , investing in index funds in the beginning , you can start participating in the capital markets and once you have a substantial base, then you can start exploring “active”  investing options.
The writeup on Types of Investors will get you to understand more about different kinds of investors.