ETFs and Mutual funds are similar, but ETFs are traded pretty much the same way a stock is, i.e. - shares. So if you like the concept of stock trading, ETFs are a natural alternative.
With a mutual fund, you buy and sell based on dollars, not market price or shares. And you can specify any dollar amount you want—down to the penny or as a nice round figure, like $3,000. With an ETF, you buy and sell based on market price—and you can only trade full shares.