John Murray
Helpful distinction: volume measures activity, not who won or what happens next. If you're comparing it with an average, check that both cover the same timeframe; a partial session isn't the same as a full day.
What is trading volume, and why did people point to it after Thursday's big tech sell-off?
Discussion
Trading Volume In Plain Words
Volume is simply how many shares (or contracts) changed hands during a period, like one day. Every trade needs a buyer and a seller, so volume does not tell you who "won". What it tells you is how much activity was behind a move. A price change on light volume involved fewer shares trading hands; a change on very heavy volume means a lot of shares changed hands at those prices. Traders often compare today's volume with an average, such as the last 30 days, to see whether a day was ordinary or unusual.
A Real Example From Thursday
On Thursday, Nov 5, the S&P 500 fell 4.36% and the Nasdaq Composite fell 5.52%. CNBC reported that the Technology Select Sector SPDR Fund (XLK) dropped 8.04% and traded more than 33 million shares, more than three times its 30-day average of 9.2 million. That comparison is what makes the day stand out: not just a big drop, but far more trading than usual behind it. Volume describes what already happened; it does not predict what comes next.
There are no silly questions here. If you want to know where to find volume on a chart or what an "average volume" line means, ask below.
Sources: CNBC (Nov 5, 2026), Fox Business (Nov 5, 2026), AP (Nov 5, 2026).