Breakpoints are a debugging tool that allow you to stop the application at a specific place in the code when it is run. When the debugger hits a breakpoint, the application is stopped and is only resumed when you either step through the code manually or you allow it to Continue.
To set a breakpoint, click inside the bar to the left of the numbers where you would like the code to stop. Breakpoints cannot be set on lines that do not have any code on them, but can be set on lines that have curly braces.
When you click the Start button to run the application and click the button that runs the code in whatever event handler the breakpoint is in, the debugger will stop at the breakpoint.
There will be a yellow arrow called a 'pointer' that signifies what line is about to execute. The idea that the debugger only executes a line of code after the debugger steps over it is an incredibly important concept that will reappear many times throughout this course.
If a breakpoint is not being hit it can either be that the button being pushed isn't correct or there is an error in the code that is not running the line of code the breakpoint is on.
To remove a breakpoint, simply click the breakpoint and it will be disabled. You can also press CTRL+SHFT+F9 to disable all breakpoints.