Use of !this

1

Dear people, been given this code below which evaluates whether an on press has occurred. It works fine but I’m perplexed by the use of (!this.clicked) why the use of !?
Why doesn’t a simple (this.clicked) evaluation work in this situation? What am I missing here guys.:hair:

  target1.onPress = function() {
        if (!this.clicked) {
            this.clicked = true;
         
            score_track =+ 1
            
            this.gotoAndPlay(2);
        }
        
    }

many thanks
julie
x