Search volume is an estimate of how many times a keyword or phrase is searched over a given period, typically reported as a monthly average.
Every search volume number you see from any tool (Google Keyword Planner, Ahrefs, SEMrush) is an estimate, not an exact measurement, and different tools regularly disagree with each other by a meaningful margin for the same keyword. Treat search volume as directional evidence of relative demand between keywords, not as a precise forecast of traffic you'll receive if you rank.
Volume also says nothing about competition or commercial value on its own — a 500-search-per-month keyword with obvious purchase intent and weak competition can be worth more than a 50,000-search-per-month keyword dominated by huge, unbeatable competitors.
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