The iPhone X comes with the 5 watts USB power adapter, which allows you to charge the phone in slow speed, not that fast speed that the iPhone X is capable of. To take advantage of the fast-charging capability of the iPhone X (or iPhone 8 and iPhone 8 Plus for that matter), you'll need to purchase extra accessories which don't come bundled with the phone itself.
If you have the MacBook Pro, you can use the Apple 60W MagSafe Power Adapter which uses a USB Type-C connector. This will enable quick charge with the new iPhone X. Keep in mind that the iPhone X comes with a Lighting port not a USB-C port. This means that you'll also need (if you haven't got one) to purchase a USB-C to Lighting Cable from Apple. Connect the USB-C connector to the MegaSafe Power Adapter and the Lighting connector to the iPhone X port and enjoy quick charging.
In this video by Unbox Therapy, he also recommended a 3rd party accessory Innergie USB-C Laptop Adapter 60W. This is an ultra compact with a foldable plug that will allow you to enable Quick Charge on your iPhone X. It also works with other devices like the Nintendo Switch, tablets, laptops, etc.
This is quite upsetting to hear that even after spending $999 or more on a phone, you don't get to have the complimentary accessories that enabled you to enjoy this very useful Quick Charge feature. You might expect to add around $70 or more to your purchase if you want to take advantage of the fast battery charging option that the iPhone X comes with.
Oh, by the way, Apple calls this "Fast-charge" or "Fast-charge capable", I've just checked it on the official website. It can charge your iPhone X up to 50% charge in just 30 minutes. This is a really important feature that I'm sure everyone would want to get advantage of. It's certainly a disadvantage not having those accessories as part of the bundle and I wish Apple had put it inside the box so Fast-charge would have worked straight out of the box.