The document discusses teacher expertise and how it can be developed. It describes the characteristics of expert teachers, such as highly structured knowledge and the ability to problem solve efficiently. Expert teachers know how to structure their content knowledge and can recognize patterns in the classroom. They are selective in what they pay attention to and have better improvisational skills. The document also examines the implications for professional development, noting that frameworks alone don't capture expert teaching and that teachers need to engage in reflection and deliberate practice to improve, such as getting feedback and observing other teachers. Both self-directed learning and managed training can help teachers develop their expertise.