What is Ad Hoc Query?

Question

I'm reading a book about SQL. In that book there's the term _Ad Hoc Query_, which I don't understand. What exactly is an ad hoc query?

Answer 1

An ad hoc query is one that is created at the time information is needed, verses a query that is already built and used routinely.

In other words “on the fly”, query. There is no technical difference between the two.