The term "query"  was define by Oxford Languages ask a question about something, especially in order to express one's doubts about it or to check its validity or accuracy. In technical term, the vocabulary "query" is also the same.

So when you should only use a query as a source for a form?

You will use query as  source if you like to ask something like show me the state of all the customers from New York or California and is Active and you want to retrieve that information and bind that to a form or a report.

For a data entry form, it's better to use just one table as the record source, which can be a single table or a query made of a single table.  The reason is that a single table ensures the form will be updateable.