Generally speaking, pedagogical knowledge is knowledge the teacher uses to facilitate students' learning. Pedagogical Content Knowledge is in two major forms - teachers' knowledge of the students' pre-conceptions and teachers' knowledge of teaching methodologies. Students come to class with a host of pre-conceptions relating to the things they are learning. The pre-conceptions may or may not be consistent with the actual subject-matter that is delivered. Teachers must have a good idea of both kinds of preconception, in order to help students, replace the inconsistent pre-conceptions or build upon the consistent pre-conceptions to bring about meaningful learning. Teachers must have a repertoire of teaching methodologies for facilitating students' learning. When the methodologies are applied wrongly little or no learning occurs in students. In effect when either of the two is weak, the teacher becomes a bad one because that teacher will not be able to execute his/her responsibility in the vocation he/she has chosen. Due to this during teacher preparation, Pedagogical Content Knowledge is emphasized.
Teachers gain Pedagogical Content Knowledge from various sources. Friedrichsen, Abell, Pareja, Brown, Lankford and Volkmann (2009) distinguished three potential sources of Pedagogical Content Knowledge. They listed the sources as professional development programs, teaching experiences and lastly teachers' own learning experiences. During their days as students in teacher education programs, teachers are assisted in variety ways to gain Pedagogical Content Knowledge. For examples, during practice, they learn how to put the pedagogical skills they learnt. Teacher education programs and other professional development programs create avenues for teachers to gain pedagogical content knowledge through workshops, lectures, working together with colleagues, and in teaching practice. Then their experiences in their classrooms as they teach students lead them to gain insight into which methodologies work under best under specific situations. That last source is usually ignored. It indicates that the professional knowledge of the teacher begins to develop long before the teacher becomes a candidate entering into teacher education. This means, the way teachers teach influences to a large extent the prospective teachers' professional knowledge and beliefs. This type of learning is, generally, overlooked by teachers at all levels because unintentional and informal, it is.
Pedagogical Content Knowledge can be gained through formal and informal means. Learning opportunities for pedagogical content knowledge, formally, designed by institutions, based on learning objectives which generally are prerequisite for certification, constitutes the formal means. In formal learning, students have clear ideas about the objective of acquiring pedagogical skills. Informal learning, on the other hand, is not organized intentionally. It takes place incidentally and so can be considered as 'side effect'. As Kleickmann et al (2012) described it, it has no goal with respect to learning outcomes, and it is contextualized to a large extent. This is often called learning by experience. Informal, but deliberative, learning situations exists. This occurs in situations such as learning in groups, mentoring, and intentional practicing of some skills or tools. Werquin (2010) described informal, but deliberative, learning as non-formal learning. Unlike formal learning, non-formal learning does not occur in educational institutions and does not attract certification. Whether pedagogical content knowledge