a Call Stack is a special stack which stores information about the functions/subroutines in a computer program which are currently being executed. It is a stack because when one function calls another, rather than simply jumping to another part of the program.

We can see a call stack in Komodo. Clicking on entries in the Call Stack will cause the text editor section to jump to that particular function definition.

Here we can see that the main section in file index.php at line 15 called the function menu_execute_active_handler in file menu.inc at line 396. The Call Stack helps you to follow the flow of execution of the program.