The video explains how to use Document Editor to build a customized document. It starts off with a description of the main sections of document editor:
1. The accordion on the left side of the document editor
2. The layout area, where the content of document is defined
3. The grouping panel, which creates custom headers and footers
The video then continues with detailed descriptions of each of these sections including information on what kind of data can be placed in each part of the layout area.
