What's the difference between Html.RenderPartial() and Html.Partial()?
Html.RenderPartial() is an HTML helper method that was introduced in MVC1 and writes directly into the response object.
Html.Partial() is an HTML helper method that was introduced in MVC2 and like the other HTML helper methods returns a string and does not write into the response object.
Both helpers are used with partial views (sometimes still called controls) to implement the DRY principal of shared View code across multiple pages.
In the MVC WebForms View Engine views have the extension .aspx and partial views .ascx. This makes it easy to distinguish between views and partial views. In the MVC Razor View Engine both views and partial views have the extension of .cshtml. In order to easily distinguish between a view and a partial view in your project I suggest that you precede the partial views name with an underscore.