There are so many external links, it's easy to get lost in this article. Look under content for the section titled "1. A Thinking and Recording Tool: Decision Records." It's under "The Four Supporting Elements." Here's a direct link if it's easier https://martinfowler.com/articles/scaling-architecture-conve... (Just search on that page for "The Four Supporting Elements)

There Harmel-Law defines ADRs as "lightweight documents, frequently stored in source code repositories alongside the artefacts they describe." He also provides a handy "Elements of an ADR" table. Let me know if you're still having problems finding it.