this vs $(this)

this vs $(this)

I have merged example code that uses "this" in two ways and I do not understand which is correct and when to use each:

            $('input[type="text"].requiredText').each(function(){
                if (this.value == '' || this.value == 'Required'){
                    this.value = "Required"
                    $(this).css({'color':'#C0C0C0'});
                }               
                $(this).blur(function(){
                    blnTextHasFocus = false;
                    if (this.value == '') {
                        this.value = "Required";
                        $(this).css({'color':'#C0C0C0'});
                    }
                });
                $(this).click(function(){
                    blnTextHasFocus = true;
                    if (this.value == "Required") {
                        this.value = ""
                        $(this).css({'color':'black'});
                    }
                });                                
            });

Can someone please clarify the differences and when to use $(this) vs this? Strange, in the 4 books on jQuery I own, none discuss "this" and it seems to be very important.

TIA,
John