You can find 3 files in "events" folder .
There are some functions in this files that can be modified by you .
For example , if you want to do some operations on "user_deleted" event . Maybe , you would like to log this operation. To do that you can modify this function in this way .
// $id is id of user that has been deleted
$log_text = "User has been deleted by $id ";
db::exec_sql("insert into logs (log_text) values('$log_text') ");
Or you just want to do something when user clicks "Start" button on "assignments" page . Then , you can modify this function in this way .
// $id is id of assignment that will be stoped
// do some operations here
All other functions you can find in that files .