Plugin

A plugin is a piece of software that adds a feature to an existing system. Instead of building everything from scratch, you install a plugin to do one specific thing.

Think of it like adding an app to your phone. Your phone can already call and text. But if you want to track your sleep, you install a sleep tracking app. That app is a plugin — it adds one feature to the existing system.

WordPress is famous for its plugin system. There are plugins for contact forms, online shops, speed optimization, security, and almost anything else. ACF, which I use for custom fields, is a plugin.

The downside of plugins: every plugin adds code, and code adds weight. Too many plugins can slow down a website. That is why I prefer to write custom code when possible — only what you need, nothing extra.