What is the difference between form constructor and load event?

In the form object, both the constructor and load are executed successively. In general, constructors are prior to load events. Both processes can execute our CodeBut the effect is often different.
I am using the autoresizecloumns method of the datagridview just now. I do not know why it cannot be executed. Then I added a button to call the autoresizecloumns method in the Click Event of the button to execute it normally. I checked the code repeatedly and finally found that I put the autoresizecloumns method in the form constructor. When I move it to the load event, it can be executed normally.
The problem is that, in general, the code we want to execute during form loading is better to be executed in the load event. But when is it necessary to execute it in the constructor?