Dubbed 1.1.1.1, the app doesn’t do anything different if you were to change your DNS manually. However given that changing your DNS isn’t exactly something that everyone knows how to do, the app simplifies the entire process by basically turning it into a toggle where you can choose to turn it on or off.
As to why you might choose to use Cloudflare versus Google, considering that Cloudflare is used by many websites and servers, using their DNS could in theory allow for faster connectivity speeds to those websites. The company is also claiming that using their DNS prevents your carrier from tracking your browser history, and that information stored on its servers will be deleted after 24 hours.
They have even hired KPMG who will perform an annual audit of the company to prove that they do indeed do as they claim. For those who are interested, the 1.1.1.1 app is available for free on both iOS and Android.