Personas are used as part of User Centered Design methodologies.  They are detailed profiles of fictional characters which represent a specific segment of users within a targeted demographic.  For this reason, analyst and designers typically use personas together with market segmentation.  They are intended to help application designers fully envision and understand the different attitudes and behaviors of users within various demographic segments.

While a persona should capture any information that is relevant and necessary for reflecting the demographic which they represent, here are a few things that can be used to build a foundation for a persona:

Persona Image – a representative picture is typically used to create a sense of realism and to give designers a firm anchoring point for the persona within their mind.
Attributes – differentiating characteristics which reflect the particular demographic that the persona represents.

Goals – what the persona is trying to achieve.

Skills – specific abilities the persona may have.
Behaviors/Desires – what types of behaviors does the persona show and what motivates the persona to act a specific way.

Character — describes details (perhaps a fictitious but believable story) about the persona to add a sense of realism.

Location/Environment – describes the surrounding environment that the persona functions within, since these environmental factors can have such a large influence on a demographics behavior.

Personas are not usually more than a page or two in length.  They are useful for considering the desires and limitations of different demographic segments in order to help guide product or application design decisions regarding features and user interactions. They can be printed and hung on the wall for all analysts and designers to see and be reminded of as they complete their day-to-day activities.