What is jQuery Unobtrusive Validation?

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?

Is there any drawback to set ClientIDMode = Static on every object ( set on maincontent of master page)

I am working on asp.net project and each time i need to use jquery identifier $(#”objectID”). I have to change the ClientIDMode on each object to be static. Since I have noticed that the default client ID mode is Inherit so i set the MainContent Client ID mode to be static and i have found that all the object became static.