Working memory is a subset of executive functioning, where you are able to hold all the necessary bits of information required to complete a complex task without losing the pieces or forgetting them, etc.
When I think of this skill I think of someone juggling and each ball signifying something that needs to be remembered. When working memory is going well, you are keeping all the balls up in the air effortlessly. When it is not, you are having a hard time keeping the balls in the air.
Enjoy!
https://www.psychologytoday.com/blog/the-athletes-way/201504/motor-activity-improves-working-memory-in-children-adhd