Page Object is a Design Pattern which has become popular in test automation for enhancing test maintenance and reducing code duplication. A page object is an object-oriented class that serves as an interface to a page of your AUT*. The tests then use the methods of this page object class whenever they need to interact with that page of the UI. The benefit is that if the UI changes for the page, the tests themselves do not need to change; only the code within the page object needs to change. Subsequently, all changes to support that new UI are located in one place.
The Page Object Design Pattern provides the following advantage: there is clean separation between test code and page specific code such as locators (or their use if you are using a UI map) and layout.
*AUT: Application under test