A UI controller hook is a certain type of extension point in the UI controller code. SAP delivers UI controller hooks to help you extend UI controller code in SAP Fiori applications.
UI controller hooks are methods in the UI controller code which are documented and kept stable. This means that any extensions plugging in are more robust across application updates.
For more information, see https://sapui5.hana.ondemand.com/sdk/#docs/guide/8fbf4e728bd146fcb2053aeb6ca741f9.html.
For more information about extending controllers using hooks, see SAP Library for User Interface Add-On 1.0 at https://help.sap.com/nw-uiaddon.