Looking under the hood of a Chrome extension - Part 1

In a recent conversation with a friend, I learned that there's a Chrome browser extension that purges Slack chat messages from the currently selected channel, and I got curious about its internals since Slack doesn't seem to offer this capability out of the box. In this series, I won't focus on the extension itself, but on the steps I took to figure out how it works, which can be helpful to understand runtime behaviours of web applications in general.