所有那些与VIX相关的ETF/ETN所跟踪的都不是VIX本身，下面是VXX的介绍

The investment seeks to replicate, net of expenses, the S&P 500 VIX Short-Term Futures Total Return Index. The index offers exposure to a daily rolling long position in the first and second month VIX futures contracts and reflects the implied volatility of the S&P 500 Index at various points along the volatility forward curve. The index futures roll continuously throughout each month from the first month VIX futures contract into the second month VIX futures contract.