I know what the jQuery Validation plugin is. I know the jQuery Unobtrusive Validation library was made by Microsoft and is included in the ASP.NET MVC framework. But I cannot find a single online source that explains what it is. What is the difference between the standard jQuery Validation library and the "unobtrusive" version?
Brad Wilson has a couple great articles on unobtrusive validation and unobtrusive ajax.
It is also shown very nicely in this Pluralsight video in the section on " AJAX and JavaScript".
Basically, it is simply Javascript validation that doesn't pollute your source code with its own validation code. This is done by making use of data- attributes in HTML.