A break point is an flag on a particular line of code. It indicates that the program should pause (not stop!) when this line is reached, right before the code on this line executes.
You can set up a break point in VB code by clicking the left-most part of the editor window. If a break point is successfully create, a red circle should display at the leftmost part of the line.
To reset a break point, click the red circle again, and it will disappear.