Definition:
GDX, the Market Vectors Gold Miners ETF tracks the performance of the AMEX Gold Miners index. The gold ETF invests at least 80% of its total assets in common stocks and ADRs (American depositary receipts) of companies involved in the gold mining industry. The investing style for this ETF is Large / Growth.
If you'd like to see more related funds, here is a thorough list of precious metals ETNs and ETFs. A List of Gold ETFs
