An item container is the item which is the immediate parent of the current item with Project Insight.
Here are a few item container types:
- Custom Items
The Item Container is represented by a Guid in Project Insight. If you create a folder or have a folder, click on the folder to view it. In your browsers address bar, the query parameter 'id' represents the Guid of the folder, which you can use to set as container when programmatically creating new items within Project Insight. All items will have a Guid associated to an item, so if you click to view a project (Task List), you'll also notice that query parameter is 'id' and represents the Guid for the project.
(Click screenshot for full image)