This is mostly a developer topic, and you shouldn't need to know specifics for the App Builder certification. But I wanted to ensure you're aware that the developer experience (DX) has been shifting much over the last year with the introduction of Salesforce DX, including new tools that work with the Visual Studio Code IDE rather than the open source Eclipse IDE. Though many still use the latter, it is no longer supported so must fall away with new Salesforce version releases. You can learn about DX with this Trail.

Get Started with Salesforce DX