In last five years or so, Exchange Traded Funds (ETFs) have grown in numbers and it asset values. In my view, ETF is another form of investing vehicle available (among many others) to investing or trading community. The major attraction for ETF has been low cost expenses and fees in comparison to mutual funds and ability in trade during market hours. Like any other investing vehicles, I believe ETFs are good vehicles depending upon how/why an individual investor uses in its portfolio. The simplicity with which you can buy and sell an ETF makes it even more difficult to understand how it is structured, what are its constituents, etc., So before you buy an ETF you much understand why you want to buy it and what role it plays in your portfolio. Broad market exposure and access to alternative assets are two important roles ETF can play in your portfolios.