December 2018
Beginner
826 pages
22h 54m
English
The main way Linux distributions are distributed is in the form of ISO images. These images can then be burned onto a DVD as appropriate, or mounted for a VM to boot from.
Head over to https://centos.org/download/ and have a look at the options on offer.
I'm going to download the Minimal ISO, for reasons that will become clear shortly.
Clicking through should bring you to a mirror page:

This is a bandwidth-saving measure on part of the CentOS Project by prompting the end user to download from any number of different hosts. They can spread the cost of bandwidth out to volunteers.