The index parameter specifies the desired item in a collection in a way that depends upon the
nature of the collection.
In any case, the index parameter can be a serial number of desired item, starting from one. Some
collection, like Columns and Rows
have a natural items order, other collection keeps the order that the items were created. There
are also such collection, like Shapes and ShapeRange,
that the order of items is unpredictable.
If the member of collection has its own name (generally accessible by the Name
property), it can be used as an index for choosing the desired item.
The TableColumn object in a Columns
collection can be accessed using either its number or associated physical Quantity.
If the index parameter is omitted, the very first collection element will be returned.