At their core, keyword research tools answer one question: what are people searching for, and is it worth trying to rank for it? They do this by aggregating search data from multiple sources — including Google's own keyword planner API, third-party clickstream panels, and web crawl indexes — and presenting it in a format that's easier to act on than raw search console data alone.
When you enter a seed term like "tax software for freelancers," a keyword tool returns a list of related queries, along with estimates for:
- Monthly search volume — how many times that term is searched in a given month (averaged over the trailing 12 months in most tools)
- Keyword difficulty — a score indicating how hard it would be to rank on page one, typically based on the authority of pages currently ranking
- Cost-per-click (CPC) — the average bid advertisers pay in Google Ads, which signals commercial intent even for organic research
- SERP features — whether the results page shows featured snippets, image carousels, local packs, or other elements that affect click-through rates
The output isn't a guarantee. Volume figures are estimates extrapolated from sample data, not exact counts. Two reputable tools will often show different numbers for the same keyword. That's not a bug — it reflects different data sources and calculation methods. The value is directional: a term showing 8,000 monthly searches is meaningfully more searched than one showing 80, even if the exact figure is off.
What these tools cannot do is tell you whether a keyword is a good fit for your specific site, your audience's actual intent, or your current domain authority. That judgment stays with the SEO or content strategist using the tool.