Hi jk, TNX is the CBOE 10-Year Treasury Yield Index. You can view it as the yield of bonds... when bonds go up, stocks go down, and the bond yield goes down.
The 320SMA is the green line on the website, the "slowest" one on the 5 min chart. Note that it only works on the 5 min chart, which mimics the 15 min 100 SMA at important support and resistance.
Hope this helps.
signed,
Bernard