Custom events explanation

I need explanation of a js event. I am going through youtube tutorials. Can you explain the below code which event is will fired and when

`frappe.ui.form.on('Meeting Attendee', {
attendee: function(frm,cdt,cdn) {


i am wondering how a attendee be a event? Please explain

Here, attendee is the fieldname, so when that field is changed/modified, this event will be fired.