@MacSparky I watched tour 2017 CMD-D video on workflow I thought it was very good. I’m very new to this stuff. My question is what is a variable???
This week’s episode talks about what a variable is!
Basically, a variable is a temporary container - only good for the duration of the Workflow or script is running (every time the automation, the variable starts empty), it’s giving a name to something so you can find it again 
(You could think of it as the index in an encyclopaedia, with the name of the thing, you get the location.)
Here’s the page on variables from the Workflow documentation.
If anyone else want to look at the videos from CMD-D 2017, they are here:
https://cmddconf.com/2017/videos.html
The video the @Jjm mentioned is at the end of the page.
@MacSparky I just watched this video today too. Was a great video on workflow foundations. Even having used it for a while was fun following along and making those workflows as you showed them