i want to change so ui of page in aem can any one help me understand the process
Clientlibs are used for maintaing css and js in AEM. In order to change page UI, you will have to create project specific css and keep css files in clientlibs anf then the clientlibs can be included in HTL or JSP.
You can refer
Hope it helps!
@biswaranjan1 Use the clientlibs to used CSS or less files to update the UI of the page or component.