Just like other interactive geometry software such as Cabri, Cinderella, Geogebra, Carmetal, with Dr. Geo the user creates a geometric sketch and manipulates it according to its constraints. What sets Dr.Geo apart from the other geometry software is the possibility of studying and even modifying/extending its source code while s/he is using it to create a figure.
All in all, its philosophy is also to empower the user with direct access to the Dr. Geo arcane and programming. For example, with script, one can build a geometric sketch to compute the slope at an arbitrary location of a given curve. Or the user can describe a recursive curve with Smalltalk programmed sketch.
In primary education, Dr. Geo is a nice tool to explore the geometric properties of triangles, parallelograms, squares, rhombus. Advanced users can also design interactive activities to guide the learners, it is achieved with a combined use of interactive sketch and programmed scripts to monitor the learner action in the Dr. Geo sketch. Such examples are distributed with Dr. Geo, and it was the result of pedagogical inquiries.
In secondary education (junior high), learners will explore more on the quadrilateral and triangle properties. Geometric transformations will be on the stage too as interactive sketch are very handy to explore and to learn about it.
Dr. Geo comes with a complete transformation tool set: central and axial symmetries, translation, scale and rotation are ready to use on point, straight line and curve. Dr. Geo is distributed with several examples of geometric transformation use. Video course were produced to explain possible use cases.
Senior high school teachers may even better appreciate the value of Dr. Geo, finding it useful even beyond pure mathematical subjects and into topics such as mechanics. Moreover, Dr. Geo programming is of good help to understand how numerical methods such as Newton-Raphson algorithm (for finding the zero of a function) behave in different situations, to create recursive constructions such as the Fibonacci spiral, based on the Fibonacci numbers or sequence and cobweb diagram, etc.
As you understand, Dr. Geo use cases are numerous, its only limit is the users' imagination.