I know what the tool does, I read the webpage.

Code coverage tools are generally specifically about test coverage, not which code actually gets executed or is unreachable.

Code coverage tools are for whatever you want to use them for. Lots of people use them to measure test coverage, but you can also use them to measure code usage in production. There are a variety of different ways to instrument code of various different levels of invasiveness and performance impact. Even the Linux kernel has built in instrumentation for measuring code coverage (kcov).