In the 'consecutive' model, a teacher first obtains a qualification (often a first university degree), and then studies for a further period to gain an additional qualification in teaching; (in some systems this takes the form of a post-graduate degree, possibly even a Masters).
The alternative is where a student simultaneously studies both an academic subject and the ways of teaching that subject, leading to a qualification as a teacher of that subject.
Other pathways are also available. In some countries, it is possible for a person to receive training as a teacher under the responsibility of an accredited experienced practitioner in a school.
Teacher Education in many countries takes place in institutions of Higher Education. An example of a traditional, comprehensive teacher education unit in the United States would be the Bradley University Department of Teacher Education located in Peoria, Illinois.