Difference between a Liferay Hook and Liferay EXT

Hooks is a feature to catch hold of the properties and JSP files into an instance of the portal as if catching them with a hook. Hookplugins are more powerful plugins that come to complement portlets, themes, layout templates, and web modules. A hook plugin is always combined with a portlet plugin. For instance, the portlet social-portlet is a portlet plugin for Social Office with hooks. In general, hooks would be very helpful tools to customize the portal without touching the code part of the portal. In addition, you would use hooks to provide patches for the portal systems or social office products.

EXT is used to customize and extend the Liferay portal. EXT builds a new ROOT webapp and replaces by a huge build mechanism your existing Liferay portal.
The Liferay EXT Environment is where you would ideally make changes to the portal itself. In other words, this is where you customize or “extend” the portal. You may ask, “Why can’t we just make the changes to the portal source directly?” The answer is that you technically CAN, but if and when you have to upgrade, you will have a tough time sorting out what is out-of-the-box and what is customized. EXT Environment keeps things separate.