In many Linux distros, package management tools are utilized for getting new packages and their dependencies. They are also used for In environments that has many boxes, updating packages and installing new packages may lead tremendous bandwidth consumption. In order to avoid this, it is possible to create a local CentOS Repository and add it all the machines. By using this ability, all other machines can get packages locally, means without consuming any bandwidth from outside Internet connection.
Since traffic inside a network for a limited time for updates does not lead to a problem for many local networks, it results in a observable gain in bandwidth usage of Internet connection. Especially, when local network and number of boxes getting bigger, the ratio is becoming more and more profitable.