A job aid is information used on the job that enables someone to produce worthwhile results while reducing the need to memorize how and when to do so.
As Joe Harless said, job aids tell you what to do and when to do it.
I’ve organized job aids here by type, and a given job aid can belong to more than one type–which is why you’ll see some more than once in the following lists.
Calculator job aids (helping you do math)
Checklist job aids (supporting accuracy and completeness)
Decision table job aids (if X, then do Y)
Flowchart-style job aids (like decision tables, but with boxes and arrows)
Procedure job aids (step-by-step guides to achieving an outcome)
Reference job aids (collecting and organizing info so you don’t have to)
Worksheet job aids (collecting data and prompting calculations)
Applying job aids