Welcome to the OWASP Zed Attack Proxy (ZAP) User Guide.
This is available both as context sensitive help within ZAP and online here in the wiki.
The English help files are under the /src/help/zaphelp directory, so if you'd like to make a change, create a pull request against those files, and they will be updated in the wiki.
This User Guide has been translated into many languages, all of which are available via the ZAP Marketplace.
The most completely translated guides are also available online:
You can help translate those pages into other languages via the OWASP ZAP Help Crowdin project.