This is a dedicated server which can be used for playing games online with your friends and family members. Here you can create a server cluster with the requisite amount of hardware and resources. There are many types of the server provided by various server provider which are game ready. However, the hardware and resources dependency fully depend upon the requirement of the game which needs to be installed on the server.
You must also take into consideration what does the gaming company says about the use of the licence.
Most games, like World of Warcraft and Minecraft, will not allow a person to charge people to play the game, as the game is the property of the gaming company itself.
If you have a private server, however, you can play a version of a game that deviates from the official version. Here you can charge people to play the game (although you should check the official rules first), or add character customizations or gameplay resections.
Of course, you can also simply set up a server to play with your friends.