"A persona is a user archetype you can use to help guide decisions about product features, navigation, interactions, and even visual design." (Kim Goodwin, Cooper.com)
Personas are a model used to describe users' goals, skills, abilities, technical experience and context. They are detailed descriptions of archetypical users constructed out of well-understood, highly specific patterns of data about real people. A persona is not based on an individual - it is a construct developed through a detailed process, not the result of a search for the "right" individual (see persona creation for more on this). They are used by the design team (and larger project team) to describe, and keep front and center the user(s) for whom the system will be built.
The goals of creating and using personas are to make user-centered design possible and to communicate what is being learned with the larger team. They put a face on the user - a memorable, engaging, and actionable image that serves as the design target. They convey information about the user to your product team in ways that other artifacts cannot. Personas will help you, your team, and your organization become more user focused.
"Interaction design is a complex and difficult craft and requires good tools like any other. The popularity of personas has exploded because they are the foundational tool upon which the practice of interaction design rests. Interaction design is about making a particular group of humans effective at achieving a narrow set of goals. Because using personas is a remarkably powerful technique for bringing those humans and their objectives into focus, it becomes the most critical tool for designing the behavior of software." - Alan Cooper, Cooper.com
Being user-centered is not natural
Users are complicated and varied
Those who may be doing user and market research are not typically the people who actually design and build the product
The word "user" isn't very helpful (like "injury" is to the ER)
Raw data isn't inherently useful, and neither are most reports
Make assumptions about users explicit (articulate a common language to talk meaningfully about users)
Place the focus on specific users rather than on "everyone"
In limiting our choices, personas help us make better decisions
Personas engage the product design and development team (personas are fun)
When to use Personas?
Make sense of research findings
Analyze results and identify patterns across research
Capture most important information about who they are, what they need to accomplish, their skills, abilities and pain points, etc.
Plan your product
Analyze competition through the eyes of your personas
Brainstorm possible features using your personas
Prioritize features using a persona-weighted feature matrix