Created to represent the different mental models that might use a site, brand, or product in a similar way. Personas are useful in considering the goals, needs, and constraints of humans in order to help guide decisions about a service, product or interaction space such as features, interactions, and visual design of a product.
Personas are constantly updated as more discoveries are made throughout the project. We must identify how the target audience behaves based on myriad of differences and similarities. Psychological shifts in the digital world along with new devices create new behaviors that make UX complicated.