RSI is the bright pink line. RSI determines strength in a direction. When it is above 20 or below -20, a pullback is likely - this could be a prime time to scale out of position. Remember do not enter a trade just because it is oversold, as the strength is still greatly against you.
RVI is the thin lighter line. RVI was created by Donald Dorsey to use in conjunction with other indicators. The instructions for using RVI is to sell/short when below -10 and buy/cover when above 10. Use this indicator to confirm your bias.
The purple area is the curve. This curve is used to analyze longer term trends in a chart. and RVI struggle to indicate long term trends, use the curve to confirm your bias. The curve is when above 0 and when below 0. Be cautious when trying to buy or sell it early when its falling. If it is falling and pops back up without reaching 0, it is typically indicate of a big price movement in that direction.