Beginners JavaScript question

Hello,

I am new to coding with Javascript and I am relatively understanding the new concepts I am learning, the only thing I am confused about is the method of identifying elements.

        $("#form span").hide();
        $("input,textarea").focus(function() {
            $(this).next().fadeIn("slow");
            }).blur(function() {
                $(this).next().fadeOut("slow");
            }).keyup(function() {
                //Check all required fields         
            });

            $("#email").keyup(function() {
                //Check valid email
            });

In the above code I understand the simple functions like: $("#form span").hide(); You are identifying the div id form and the span within that form and telling it to hide that element. However, when it comes to this function:

            $("input,textarea").focus(function() {
                $(this).next().fadeIn("slow");
                });

I am a little confused. I realize we are calling out the input elements on the page and that when the user is selecting the form element to fade in the span. What I am not understanding is the $(this).next() part of the code. Could someone explain what that bit of code is referring to?

Thanks for your time!