What is this field that pops up on my Work Item forms called "Parent Items?"
As the red indicator tells you, it is one of two default required fields for adding any PI item - in this case a Project Request:
PI Wants to Keep Your Team Organized
To stay organized, you are required to tell PI where this Project Request will be stored - as in which Folder:
The ONLY time PI will not ask for the Parent Item is when you are already in a Folder and you create the Work Item from that location in PI.