ASP.NET jQuery Ajax Calling Code-Behind Method

I am very new to web development, but have a lot of experience in development in general. I have an ASP page that has a few input fields and a submit button. This submit button purely calls $.ajax, which I intended to have call a method in the code-behind file. However, I’ve noticed two interesting things. First, the ajax call succeeds regardless of what data is provided to it. Secondly, the responseText field is the entire page’s html source.