Final answer:
PMD is an open-source linter with built-in rules used in Copado to maintain codebase standards, and it operates during the development phase.
Step-by-step explanation:
PMD is an open-source tool that includes built-in rules. It is commonly used within the Copado DevOps ecosystem as a linter to enforce a certain standard for your codebase. Unlike Code Inspector, which is another tool for reviewing code quality, PMD executes in the development phase to help maintain code quality by identifying potential issues before they make it to production.