There are several differences.
First, the aims of the two degrees are different. The PhD is a degree for those who wish to become university researchers in the field of education. The EdD degree in professional practice is for career professionals (teacher leaders, school administrators, clinical faculty, etc) who are looking for an advanced degree that will provide them with experience in the application of knowledge to problems of practice.
Secondly, the EdD is a cohort program that involves three years of study with a good deal of emphasis on collaborative work. In addition, each member of a cohort will advance through the program in the same sequence—taking the same courses and engaging in the same projects. Emphasis is placed on team-work as well as individual achievement.
Thirdly, the EdD is designed with the career professional in mind. Coursework is offered during the summer to coincide with the summer break, and problems of practice projects will be conducted throughout the program in the fall and spring semesters.