Difference between visual webpart and standard webpart in SharePoint

Visual Web parts provide a visual design surface in Visual Studio 2010 which allows you to drag & drop controls from the toolbox into your webpart and manipulate their properties via the designer or code-behind, so its very similar to standard asp.net page & user control development.

Standard web parts do not provide this visual surface, thus need to have their control tree built entirely in the code behind for the web part. Standard web parts also inherit directly from the asp.net Webpart control, so you'll need to add reference to the Sharepoint control library and instance to properly set your control hierachy.