Dear Damielle,
As you very well put it, practioner is "one who practises the profession" .
The noun is usually related to the expression "reflective practioner", used by Sch�n in his book The Reflective Practitioner, How professionals think in action. New York: Basic Books, Inc., Publishers, where he developed his theory and practice of learning and incorporated the concepts of reflection in action and reflection on action.
Since then, the concept affected the study of teacher education, health professions and architectural design. It is also related to some research methods such as action research, case study and educational ethnography.
As Cunlife puts it, (On Becoming a Critically Reflexive Practitioner, Journal of Management Education, Vol. 28, No. 4, 407-426 (2004):
Critically reflexive practice embraces subjective understandings of reality as a basis for thinking more critically about the impact of our assumptions, values, and actions on others. Such practice is important to management education, because it helps us understand how we constitute our realities and identities in relational ways and how we can develop more collaborative and responsive ways of managing organizations. This article offers three ways of stimulating critically reflexive practice: (a) an exercise to help students think about the socially constructed nature of reality, (b) a map to help situate reflective and reflexive practice, and (c) an outline and examples of critically reflexive journaling.
The concept, as far as teacher education is concerned, has developed, and several types of teacher reflection are considered. Neville Hatton, Senior lecturer of School of Teaching and Curriculum Studies, in the University of Sydney, defined several types of teacher reflection, such as Technical reflection, Descriptive writing, Descriptive reflection, Dialogic reflection and so on.
As Mark Haws, from Dakota State University, Department of Instructional Technology, wrote:
The call to improve the quality of inservice teacher development ardently encouraged opportunities for teachers to collaborate with peers to make sense of the teaching and learning process
Thus, practitioner refers both trainee teachers and inservice teachers.
Have a nice Sunday.