My Train Tracker allows you to document your model railroad/model train collection and layout(s). You will be adding your Items into your account piece by piece. Each Item will be added directly to one of two types of Containers, either a Layout or a Collection. When adding an Item to either a Layout or a Collection, that Item can also be assigned to a specific Container of the other type as well.
Example: - If you have a Collection named "Buildings" and a Layout named "HO Scale" and you're adding an Item to your Buildings Collection that represents a model building that resides on your HO scale layout, you can also specify that the building Item belongs to both your Building Collection and also your HO Scale Layout.