What It Is
Google Analytics is the one most businesses have heard of, because it is free and Google's own. Others do the same job, among them PostHog, Plausible, Fathom, Matomo, and Mixpanel. Each one puts a small piece of code on every page of the site, and that code reports every visit back to a dashboard the owner can open.
How It Works
The code records which page was viewed, where the visitor came from (a search, an ad, a link on another site, or an address typed in), what device and browser they used, and what they clicked. The platform turns those records into reports: visitors over time, visitors by source, visitors by page.
Counting visitors is automatic. Counting customers takes one more step. An action worth money, like a call, a form sent, or a booking made, has to be marked as one, and the platform counts it from then on, never for the visits that came before. That step is conversion tracking.
Why It Matters for Being Found
Without one, an owner knows the phone rang. With one, the owner knows which search, listing, or ad made it ring, and whether a change to the website helped or hurt. It is the record of the site's traffic kept from the site's own side, rather than what a search engine or an ad platform chooses to report about it.