In engineering, debugging is the process of finding the root cause, workarounds, and possible fixes for bugs. For software, debugging tactics can involve interactive debugging, control flow analysis, log file analysis, monitoring at the application or system level, memory dumps, and profiling.
Once a debug session starts, the Debug toolbar appears at the top of the window. The toolbar contains actions to control the flow of the debug session, such as stepping through code, pausing execution, and stopping the debug session.
In general, debug refers to examining and removing errors (bugs) from a program's source code. For example, a developer may debug a program to see where in the code an error occurs so it can be resolved or bypassed.
The Debug Control window shows that execution has moved on to the next line of code. Also, at the bottom of that window there is a pane that says "Locals" and it shows the value of radius to be '23'. This is useful in several ways. It shows the values of variables as they change, and it shows the types of variables.