Recently, while mentoring a couple of kids who are starting to learn programming (using Ruby), I encountered the challenge of explaining the %f/d/g notation for formatting data in a string.
The notation is used in converting data into representations that can be printed as (part of) a string. The operation is called string interpolation. The format is used in commands like printf, and the syntax is typically like this:
printf(<string with format specs>, data value 1, data value 2, …)