what's it in Qform

Hello everyone, I was looking at QformBase and saw these functions. But only one of these functions that I know that is the FormCreate. The other functions does anyone know what could be and its features? thank in advance.

       protected function Form_Run() {}
       protected function Form_Load() {}
       protected function Form_Create() {}
       protected function Form_PreRender() {}
       protected function Form_Validate() {return true;}
       protected function Form_Exit() {}