Structure is a database object which is a group of fields which can be used in multiple tables in SAP ABAP. The advantage of structure is that it is reusable in multiple tables. The difference between the table and structure is , structure can hold single record only where as a table can hold multiple record.

In this document, you will find step-by-step guide to structure implementation in two ways:

• Include structure: This option is used only for Custom Tables (i. e. the name starting with Z or Y). These include structure can be reusable.
• Append structure:This option used only with STANDARD SAP TABLES. The Append Structures are not reusable

1) Where do I manage this Include Structure (SE11 or SBIW)?

You can manage the include structure both places, cause you jump from SBIW into SE11.

2) Is Include Structure the same thing as Append Structure?

An include structure is NOT the same as an Append structure. I tried in a datasource to add a field via an append structure, however I didn't see the

field in the data source. When I changed it to an Include structure , everything was ok.