First, the VIX is a weighted average measure of the implied volatility of a bunch of near-term, near-the-money S&P call and put options (HERE for its calculation). To learn about the many different volatility indexes go HERE. The main appeal of the VIX as a hedging instrument for short-term traders is its negative correlation with broad-based equity market indexes.
Second, VIX futures represent the futures market view of the 30-day expected volatility or VIX.
Third, an ETN or exchange-traded note is like an ETF except that it is a debt instrument.
Fourth, TVIX is a double-leveraged version of the VIX futures contract.
Fifth, Credit Suisse that offered this product, decides last month to stop issuing more shares. When it became difficult to borrow shares, the ETN traded at a huge premium to its NAV (more like a closed-end fund).
Sixth, Credit Suisse decides to open the fund again and the premium collapses.
Seventh, long or short volatility at your own risk. GOT IT!
That said, I think VIX below 15 with earnings coming looks more like a buy than a sell to me.