What is different between WebUserControl and in WebCustomControl ?

Web user controls :- Web User Control is Easier to create and another thing is that its support is limited for users who use a visual design tool one good thing is that its contains static layout one more thing a separate copy is required for each application. 

Web custom controls:-Web Custom Control is typical to create and good for dynamic layout and another thing is it have full tool support for user and a single copy of control is required because it is placed in Global Assembly cache.