The website says there is Maths Professional Development built into the lessons. What does this mean?

All LTD lessons include a list of the maths concepts that are the focus of the lesson. They also include a brief Teacher Background section aimed at providing some insight into the Maths in the lesson. The intention of these sections is to teach the teacher something they may not have realised about the maths in the lesson. LTD lessons also model an inquiry approach so teachers can learn about this way of teaching as they become familiar with the lessons. The LTD team can also present dedicated Professional development to schools on request.