Custom controls are controls that are developed by the 
developer
or a third party vendor. Custom controls are not provided 
along with 
.NET. 

Difference between Custom Controls and User Controls.

1.User Control is a page file with extension .ascx which 
can only be used within
a single application. But custom controls are assemblies
(dll files) that can be 
used in multiple applications.

2.User Controls cannot be added to the ToolBox of VS.NET . 
To use a user Control with in an
aspx page u have to drag the user Control from the solution 
Explorer to designer page.
But Custom Controls can be added to ToolBox of VS.NET.

3.User Controls can be viewed as a sort of generic controls 
during the design time.
The proper GUI of user controls can be viewed only during 
the run time.
But Custom Controls can be viewed during the design time.

4. User controls are created from existing Webserver and 
html server controls .
But a developer who creates custom controls have to render 
every thing from the scratch.

5.Since the dll assembly of a custom control is being 
used,a custom control developed in C# can be used in a 
project developed in VB.NET or any other managed code and 
vice versa.
This is not possible with user controls.They are language 
spefic

We cannot give any examples for custom controls since they 
are developed either by a developer of a third party vendor.