MVC中部分VIews和用户控件之间的区别

Can anyone please tell what's the exact differences between partial views and user controls in an MVC app? Which one is feasible to use? I am using user controls for filling my views which have one or more tabs(which i have added using Ajax control toolkit). I want to know about advantages/disadvantages while using partial views and user controls.Can anyone please tell what's the exact differe