Structure tags
Structure tags typically represent structural information, for example, paragraph styles, anchored frames and tables. These tags and their content are completely ignored during translation and can only appear outside sentences.
The only structure tags which are displayed are the ones marking the beginning and end of a file. Certain properties of structure tags are displayed in the document structure column, for example, headings may be associated with a formatting style that is used in the Editor window.
In some cases, if there is no structure context displayed in the document structure column, the only visible impact to your document is the way that the document is segmented.