The fine thing about ETFs is that they are for investors and traders equally. You can trade them and you can grow your wealth in the long run.

Operating in the ETF markets

Another advantage is the thousands of stocks with which an ETF portfolio can be enriched or vice versa. For example, be invested in the whole market with the QQQQ and swing trade oil with DXO while at the same time trying to catch the next growth stock early on.

ETFs are like stocks but they bear in general a smaller risk. People use them for instance for their IRA account. They are not only for trading but for investing also. There are also ETFs that resemble commodities or currencies and as such they are really a valuable instrument for the trader. For leverage interested people there are even ETFs that have an options like characteristic, because they are artifically associated with a fixed price of a commodity contract or spot price. This means they can't fall below zero themselves in case the master instrument goes beyond the "virtual zero", because they are traded at stock exchanges and thus they are stocks.