It adds an additional column that displays the source URLs corresponding to each row of results.
You may want to use the showUrls option when you load various data sources so you can identify the page where each result comes from.
=IMPORTFROMWEB(data_sources, selectors, "showUrls")
or
| A | B | |
|---|---|---|
| 1 | showUrls | true |
| 2 | ||
| 3 | =IMPORTFROMWEB(data_sources, selectors, A1:B1) |