What Is the Use of UI Component in Magento 2?

Magento user interface (UI) components are used to represent distinct front-end elements, like tables, buttons, dialogs, and so on. A candidate should be able to implement them using PHTML templates with inline JavaScript, via XML layout, jQuery widgets, or UI components.

Magento encourages the use of UI components to build the UX and ensure smooth interaction of all website features, especially the ones with asynchronous initialization. They also allow a developer to create more complex UI components out of smaller components (e.g. for the store checkout page).