How does the IRS calculate taxes for ETFs? Until recently, I thought they were taxed the same as stocks, but I recently purchased a gold ETF (IAU) and have to pay a small capital gains tax even though I didn't sell any shares. Stocks are only taxed when they are sold (capital gains) whereas mutual funds can incur taxes while they are held when the underlying investments are bought and sold by the fund manager.
Which category do ETFs fall into? Does the tax treatment depend on the type of ETF? Where can I look this information up? I also own some bond ETFs and have thought about buying some real estate ETFs. Are they also taxed differently?