The Infoset Query is a subset of SAP Queries. Unfortunately, there are many SCN posts that call all the SAP Queries "infoset queries" (as opposed to QuickView queries in SQVI). It's very unfortunate verbiage choice by SAP IMHO - as if regular SQ01 queries are not based on the infosets.
There is SAP Help article on the Infoset Queries, I'd refer to it if a clarification is needed.
Unless the requirement is specifically to create the Infoset Query, I would suggest to not touch that button and instead just create a regular query (Create/Change buttons). In the regular queries, if you hit Basic List, you'll see all the fields available, with the automatically added text fields in "Additional fields" section, just like on the Sandra's screenshot.
There is a good collection of the query-related SCN blogs/documents, see here: Infoset Queries: Collection of important posts
Although, as I've mentioned, the "Infoset Queries" term is used incorrectly all over the place.