Responding to changes wpf c# using a list [duplicate]

    public event PropertyChangedEventHandler PropertyChanged; 

PropertyChanged

    public void  NotifyPropertyChanged(string a)   
    {
        if(this.PropertyChanged != null)  
        {
            this.PropertyChanged(this,new PropertyChangedEventArgs(a)); 
        }
    } 

i dont quite understand what is going on in this line

this.PropertyChanged(this,new PropertyChangedEventArgs(a));

i did understand all the above but i cant understand how this line work and i ask if i need this for wpf application im using a list of object im following this tutorial

https://wpf-tutorial.com/data-binding/responding-to-changes/

but maybe i can use other way