Trading volume is a measure of how much of a given financial asset (like a stock, bond, or futures contract) has been traded in a specific period of time, such as a day or hour. It is one of the most basic and significant parameters used in stock trading and market analysis. 

The volume of a stock can give traders an insight into the strength and vitality of a market trend. For instance, a high trading volume often means a lot of traders are buying or selling the stock, which could indicate strong investor interest and potential significant price movement. On the other hand, low trading volume may suggest a lack of investor confidence or interest.

A sudden increase in trading volume could signal a powerful move is underway, while a decrease in volume might indicate that a trend is nearing its end.