JNK is an ETF that tracks rated high-yield bonds or "junk bonds". These are the bonds rated Ba1 & BB+ by Moody's Investors Service, Inc., & Fitch Inc. respectively.
The bullish divergence with the ROC is pointing out that a bottom is near.
Bonds bottoming is a good sign for the market and breakout to the upside should confirm a healthy uptrend for stocks.
This ETF has a high correlation with the SPY; 0.7021 for the last 3 years, so, let's wait and see.