Search volume
Search volume is an estimate of how many times a term is searched in a given market each month. It is a rounded, modelled figure, not a count, and it says nothing about whether those searchers want to buy anything.
Treat it as an order of magnitude
Volume figures come from modelling, not from a meter. Different tools report different numbers for the same term, sometimes by a wide margin, and all of them round heavily.
Used well, volume tells you whether a term is worth roughly nothing, roughly something, or roughly a lot. Used badly, it becomes a target to chase.
Low volume is often better
Ten searches a month for “emergency plumber [suburb]” is worth more to a plumber than ten thousand for “plumbing”. The first group has a burst pipe. The second is a mix of students, competitors and people looking for a diagram.
Scout ranks opportunities by what they could realistically bring you, not by volume alone, which is why the list is not sorted biggest-first.