Where to use Visual Basic User Controls
User controls are a means to combine different existing controls and to provide a complex functionality in a single control. Combining different controls this way would help you to modularize your code and help you to speed up the development process.
The designers of the user interface and the coders can work separately in this process whereby each will be doing their job efficiently.
For example if you are to provide a form that has a number of textboxes and labels, which are used to get some standard input from the users, then you can combine these textboxes and the labels to form a user control and then apply the styles to them too.
This would give them a unique look throughout your application. By creating such user controls you can use the user control wherever you want with ease. User controls are created as DLLs in the bin directory of the application.
You can simply add this DLL to the toolbox using the customize option of the tool palette. After you add the user control to the tool palette you can use it as you use the other controls available in the toolbox.