Refer the below link. You can find the explanation here --
Migration Guide to CoralUI 3-based — Granite UI 1.0 documentation
The new set will not use the layout concept anymore. This is to increase the simplicity of the understanding of Granite UI. Each layout component thus becomes a standard component.
The layout mechanic itself is still there for other to use if needed.
Before:
+ mytabs - sling:resourceType = "granite/ui/components/foundation/container" + layout - sling:resourceType = "granite/ui/components/foundation/layouts/tabs" + items + tab1 - jcr:title = "Tab 1" - sling:resourceType = "granite/ui/components/foundation/container" + tab2 - jcr:title = "Tab 2" - sling:resourceType = "granite/ui/components/foundation/container" + layoutConfig - active = true
After:
+ mytabs - sling:resourceType = "granite/ui/components/coral/foundation/tabs" + items + tab1 - jcr:title = "Tab 1" - sling:resourceType = "granite/ui/components/coral/foundation/container" + tab2 - jcr:title = "Tab 2" - sling:resourceType = "granite/ui/components/coral/foundation/container" + parentConfig - active = true