Educational psychology is a very broad topic. It is also very important. For these reasons, entire courses are devoted to its study in teacher training programs around the United States.
Psychology, of course, is the study of people’s mental processes and their behaviors. Educational psychology is the study of psychology within the context of teaching and learning. Educational psychology seeks to study the processes by which students learn so that it can identify what ways of teaching and learning are most effective.
A course in educational psychology covers a wide range of topics. It will typically cover child development so that teachers can better understand how students of different ages will behave. It will study how students interact with their peers since this can affect their behavior in the classroom. It will cover the idea of multiple intelligences so that teachers can understand that different students might be intelligent in different ways. It will cover the nature of learning, the nature of memory, and how critical thinking occurs.
In other words, educational psychology courses cover every aspect of how children and young adults think, behave, and learn.