Automation coverage
Automation coverage is the share of documented test cases that are executed by automated tests rather than by people. It is usually reported per project, suite or release, sometimes weighted by priority. The figure is only trustworthy when automated results are mapped to test case records, so a case counts as automated because a result was recorded against it.
How it differs from code coverage
Code coverage counts lines, branches or functions of the application that tests execute. Automation coverage counts documented test cases that automated runs execute. The two answer different questions. Code coverage tells developers which code no test touches. Automation coverage tells a QA lead how much of the planned testing still needs a person, which is the number that drives regression effort and release timing.
How it is calculated
The simplest version is automated cases divided by all active cases in scope, for a project, a suite or a release. Useful variants weight the count by priority or risk, or split it by suite, because 60% automation of low-priority cases and 60% of critical paths are very different situations. A case counts as automated when an automated result has actually been recorded against it in the chosen period, not when someone ticked an "automated" flag.
What makes the number honest
Automated results have to map back to test case records, usually through a test case ID in the automated test. Without that link, the number is either a manual estimate or a flag nobody updates. Tests in quarantine deserve a separate line, since they run but no longer protect the build. How the report works in practice is in automation coverage reporting.