Object Recognition (3D Scan) enables you to create apps that can recognize and track objects, such as toys. This article will show you how to add Object Recognition and Object Targets to a Unity project, and how to customize the behaviours exposed through the Object Recognition API and also implement custom event handling. If you have a 3D model already for the objects you are looking to track, Model Targets provides a very robust tracking solution which does not require the object to be scanned.
If you are unfamiliar with the Unity Workflow, it may be helpful to read Getting Started with the Unity Workflow
You will also need to get a license key from the License Manager and add it to your project if you are looking to track your own objects. The following articles may be helpful: How To Create an App License and How To add a License Key to your Vuforia App