Search volume
Search volume is how many times people search a keyword in a month, on average. It's the usual way to size demand in SEO.
Search volume is how many times a keyword is searched in a month, usually averaged over a year. It's the first number most people look at in keyword research, because it tells you how many people might want what a page offers.
For a marketer, search volume sizes the prize. A phrase searched 20 times a month can still be worth a page if the people searching it are ready to buy, but it can't carry a whole campaign.
Where the numbers come from
Google shares volumes with advertisers in Keyword Planner, grouped into ranges unless you spend on ads. SEO tools build their own estimates from that data and from panels of browsing data, so the same keyword can show different volumes in different tools. Treat them as a rough sense of size.
Volume also hides how many searches end in a click. Some searches are answered on the results page, so the visits on offer can be far fewer than the volume suggests.
Volume for AI prompts
Nobody publishes how often each question is asked on ChatGPT or Perplexity. And questions to AI platforms are long and personal, so almost every exact wording is asked rarely. "Best coffee subscription for a small office in Leeds" might be asked a handful of times a month, while the need behind it comes up all the time in hundreds of different wordings.
So for AI search, it helps to size the subject and then track a few typical questions about it. For example, Fernhill Coffee might find that "office coffee" comes up often across the platforms and track five prompts that ask about it in different ways.
In AnswerOrbit
The Demand tab in Topics shows an estimate of how many conversations a month use a word or phrase on the AI platforms, how that changed over 12 months, and the related questions people ask. It's an estimate from a panel of conversations and searches on the six platforms, and it can be up to two weeks behind. Each prompt shows its demand as one of five levels, from Lowest to Highest. See Topics and prompts.