Monetization is the way to get income on YouTube. It can be achieved in different ways.
AdSense is a process that was created by Google on 2003. It is used on YouTube now. By adding your AdSense account you let comercials be in your video
Patreon is a website that lets users donate to their creators, This is not supported by YouTube, but is famous on YouTube and other creators on the site
YouTube partners like Machinima or Socialblade are networks that give money to their creators, but the creators need to have some requisites to do. The first one was created on 2010, and its the world famous Maker Studios.