In my 28 years of teaching elementary school, professional development has evolved in several ways. In earlier years, the teachers would be subjected to a subject that may or may not have relevance to their actual teaching. Each staff development opportunity would be an isolated, stand-alone hour or two with no follow-up to check understanding. Nobody bothered to check with the teachers to see what, if anything, they had taken from the classroom and at least attempted to practice in the classroom.
Today, professional development provides teachers with ongoing and relevant training in best practices for instruction, assessment, and collaboration among educators to improve student learning and classroom teaching. Professional development is ongoing training that is provided to enhance student achievement. There is follow-up checking for understanding that demonstrates how well the teachers are able to improve instruction.
Professional development is professional learning. As teachers practice their craft, they learn to incorporate the latest state-of-the-art instructional methods demonstrated to assist each student in the methods which are their strengths in learning. Teachers collaborate, share best practices, and learn from each other. Teachers learn to move beyond their isolated classroom to work with all students at their grade level and subject area. Collaborating with colleagues spreads the stress around, reducing it for all.