It is a market breadth indicator. For calculating the strength of the market, the Open-10 TRIN function uses declining or advancing volume and declining or advancing issues.
Very low values may show that the market is becoming overbought and a sell-off should happen in the nearest future (which will result in the prices' decrease). In the same way, very high values can show an oversold market. Readings less than 0.90 are bullish. Readings that are more than 0.90 are bearish.
It is important to remember that the running totals have the same effect as taking a moving average of every parameter as the division by the length of every average cancels out. The ratio of advancing to declining issues is afterwards divided by the ratio of advancing to declining volume.