We're starting here with some basic definitions available on the web.

Basic definitions (where does all this come from):

Personas are fictitious characters that are created to represent the different user types within a targeted demographic that might use a site or product. Personas are most often used as part of a user-centered design process for designing software or online applications, in which the goals, desires, and limitations of the user are considered when designing the product. (http://en.wikipedia.org/wiki/Personas)

A scenario is a narrative describing foreseeable interactions of types of users (characters) and the system. Scenarios include information about goals, expectations, motivations, actions and reactions. Scenarios are neither predictions nor forecasts, but rather attempts to reflect on or portray the way in which a system is used in the context of daily activity.  (http://en.wikipedia.org/wiki/Scenario_%28computing%29)

Further readings:

on usability.gov - basic definitions
on cooper.com - extended info and articles
on boxesandarrows.com  - critiques and thoughts 

Our definitions (what we want/need to do):

To avoid to be swamped in the complexity of the task.

>>> (lili) :
    We want to have simple Carachters (personas or profiles) that can be put on a Stage (act in a narration or behave in in use-cases);
    personas should not be overdetailed, just good enough to be plausible actors in a scenario  (people-software or people-people)
    My idea of the process  is something like:   brainstorm (here or mailing list ) - sketch (on the contribution pages) - review (using comments or mailing list )

>>>  (proposed by djay):

    We want to collect real stories that are inspiring, funny, representative of your experience.
    Real stories are easy to write and always good to tell to partners/customers/collegues (as suggested in Mark's Marketing ReMarks at the PSPS..)

... your aim?

    write down here or let's discuss in mailing list

 

Examples (what some others are doing):

Drupal does it!:  http://groups.drupal.org/node/3761
profile for all the various "types" of users of drupal/drupal website

Basket software: http://basket.openusability.org/wiki/index.php/Persona_overview
Personas created for  Basket, a multi-purpose note-taking application for the linux desktop

CMSConsultant website: http://www.cmsconsultants.org/resources/website/personas
Example of archetype users for a site addressing CMS consultants. Made simple and quick.