The Put-Call ratio is the ratio of the volume traded of put options to the volume traded of call options.
The Put-Call ratio is a trading indicator derived from the options market and used by traders as a market sentiment tool. It is used to gauge the general market sentiment as well as the sentiment of individual securities.
As an example, a stock trader can use the Put-Call ratio of a given stock, which the volume of put options traded for that particular stock divided by the volume of call options, to gauge whether investors view of that stock is bullish or bearish.