TL;DR Volume is the number of shares traded in a period. Price tells you what happened; volume tells you how many people meant it.
The plain-English version
Every trade has a buyer and a seller, and volume simply counts the shares that changed hands — per day, per hour, per candle on the chart. A stock that trades 40 million shares a day is a highway. One that trades 30,000 is a dirt path where your own order is a traffic event.
Why care? Because a price move without volume is a rumor, and a price move on huge volume is a statement. If a stock jumps 8% on triple its normal volume, real money repositioned. The same jump on a dead-quiet day can be a handful of trades in a thin market — noise wearing a suit.
What traders actually check
- Relative volume (RVOL) — today's volume versus its average. RVOL of 5 means five times the usual crowd showed up; something is happening. It's a core scanner filter for day traders.
- Volume on breakouts — a stock pushing past a key level on big volume is far more trusted than one drifting through it on nothing.
- Volume on the way down — panic has a signature: huge red days on huge volume. So does capitulation, sometimes marking bottoms.
Liquidity: the practical reason you care
Volume determines how easily you can get out. High-volume stocks have tight spreads and instant fills. Low-volume stocks punish you twice — a wide spread on entry, and a vanishing bid when you need to exit. Position sizes that are trivial in liquid names can be traps in illiquid ones. (This is also penny-stock scam mechanics: it's easy to push a price up when almost nothing trades.)
The common mistake
Reading price charts while ignoring the volume bars underneath. Beginners see "stock went up" and assume demand. Volume is how you check whether anyone actually voted — or the room was just empty.
Educational only — not investment advice. Price is the headline; volume is the fact-check.