Exploratory has no definite starting and stopping point for the student. The student can branch from one area to the next. Most websites are a perfect example of this. You have several hyperlinks on a page that you have to choose to branch into different pages or sites. Exploratory is great for developing student creativity and concept discovery.
Students learn well when they discover things on their own.
Since exploratory type of instruction is very unstructured, students may not be learning the musical concepts you want them to. Regimented is the opposite of Exploratory. Regimented has a definite starting and ending point and is very structured. Students can't veer off into unwanted directions. Drill and Practice is very regimented.