Personas are made up people who would be associated with your business. These 'made up' people would ultimately be based off real people in the real world. For example a persona for ‘Amazon Prime for Moms’ would have a persona as a mother who has 3 kids and is always shopping for toys online. The ads and landing pages would be targeted towards toys for kids.
Studying and creating new personas is key to understand your business even more. Upon making personas new fresh ideas will come to you that you normally wouldn’t think about until you make that persona.