The backtrace area displays the function calls on the execution stack.
Each expandable item in the backtrace area represents a stack frame associated with a function call.
Double-clicking on any stack frame finds and displays the source code definition for that function in the Editor, if this is known. Any frame selected in this area can be operated on using the commands in the Debug > Frame menu: See Performing operations on stack frames for details.
Expanding a stack frame displays any variables associated with that function call. You can double click on any variable to inspect the variable using the Inspector tool. Any items selected in this area can be operated on using the commands in the Debug > Variables menu: see Performing operations on frame variables for details.