The COT data, released each week by the CFTC, provides a snapshot of different types of investors in the futures markets. They are categorized into three distinct trader groups called the non-commercials, commercials and the non-reportables. The CFTC places traders into these groups based upon their reasons for taking futures positions and by the size of the positions these traders take.
Open Interest is a key component to price trends and a gauge to whether the trends are gaining steam, losing steam or could be ripe for a trend change. High open interest simply means there are many more opinions (long and short) in the market while low open interest is evidence of less enthusiasm about that particular market.