The charge tax feature lets you add tax to your bundles in BundleBuilder. So, when customers buy a bundle from your store, they'll also pay the tax on it.
Using this feature is important because it helps you follow the rules and regulations for selling online. In many places, you're required to charge tax on the things you sell. So, by using Charge Tax in Bundle Builder, you make sure you're doing things the right way.
If you need to learn more about taxes on Shopify you can visit the following link: https://help.shopify.com/en/manual/taxes
It's a simple step that can make a big difference in how you run your Shopify store.