Search volume is the number of times a query is searched in a given market per month. It's the most visible keyword metric and often the most misused.
Most SEO tools pull volume from Google Ads' Keyword Planner (with bucketing + estimation) or from clickstream data providers. Neither is exact. Expect ±30% error for medium-volume queries and ±50%+ for low-volume ones.
Volume is a rough magnitude indicator, not a precise forecast. "1,000/mo" vs "1,200/mo" is noise. "1,000/mo" vs "10/mo" is meaningful.
Many queries have strong seasonal patterns. "Christmas gifts" peaks in November-December, troughs in summer. Averaged "annual" volumes hide this. Check seasonality explicitly via Google Trends.
If your business is US-only, global volume is irrelevant. Always filter to your target market in your tool of choice.
A query with 10,000/mo volume but heavy SERP features (AI Overview, PAA, knowledge panel) might send only 500 clicks to the top organic result. A query with 1,000/mo volume and no features might send 270 clicks. Adjust your volume estimates for CTR share.
Tools like Ahrefs show "Global Search Volume" AND "Clicks" (estimated real clicks to the top results). Clicks is usually a more honest metric because it already factors SERP features eating CTR share.