As mentioned on Wikipedia, Mike Krzyzewski is Christian. However, inside Christianity, he follows the catholic religion through a succession of Pope.

On simpler telling, Christianity is the core Abrahamic religion, comprising various following faiths as Catholic Church, Lutheran Church, Eastern Orthodox Church, Protestantism, and Methodism.

All Catholics are Christian, but all Christians are not catholic. The term seems similar yet different at the same time. 

Mike, following Catholicism, strongly believes to be derived from sacred scriptures and sacred tradition.

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