Bootstrap is a complex front-end solution, which includes CSS, JavaScript, fonts and so on. In order to allow you the most flexible control over Bootstrap components, this extension provides several asset bundles. They are:
- [[yii\bootstrap4\BootstrapAsset|BootstrapAsset]] - contains only the main CSS files.
- [[yii\bootstrap4\BootstrapPluginAsset|BootstrapPluginAsset]] - depends on [[yii\bootstrap4\BootstrapAsset]], contains the javascript files.
Particular application needs may require different bundle (or bundle combination) usage. If you only need CSS styles, [[yii\bootstrap4\BootstrapAsset]] will be enough for you. However, if you intend to use Bootstrap JavaScript, you will need to register [[yii\bootstrap4\BootstrapPluginAsset]] as well.
Tip: most of the widgets register [[yii\bootstrap4\BootstrapPluginAsset]] automatically.