YouTube is a video sharing platform launched in 2005 that allows users to discover, watch and share originally created videos. It has over 490 million unique users monthly and racks up 92 billion views each month. YouTube provides easy, free access and the potential to build a global brand or cause offense depending on the content. Key metrics for measuring performance include video views, subscribers, engagement and comments. Users can create accounts and customize channels to promote their personal brands. Companies have successfully used YouTube for advertising through various formats but must present themselves positively to avoid backlash.