A concordance line brings with it information about which segment of the text it was found in.
In the screenshot below, a concordance on year was carried out; the listing has been sorted by Heading Position -- in the top 2 lines, year is found as the 3rd word of a heading. The advantage of this is that it is possible to identify search-words occurring near sentence starts, near the beginning of sections, of headings, of paragraphs.
See also: Start and end of text segments.