How to Use ObjectManager?

• Instantiation and configuration of an Object via two main methods: GET and CREATE.
• Singleton pattern implementation.
• Dependency management.
• Automatic initialization of parameters.

Why is this one of the Magento tricky questions? Because ObjectManager is never used directly in classes/templates. A Magento developer should know that, if referenced directly, ObjectManager will break dependency injection principles, make code testing more difficult, and breach best coding practices.