It's something that I've found challenging to communicate to the children. I'm focusing on improving this at the moment. In order to do so, I did a very simple thing - I stuck the key concepts to the bottom of the whiteboard. I always write the learning objective(s) on the corner of the board. Now, given the position of the key concepts, I can easily ask the children to identify what concept(s) we are exploring and place it near the objective.
I know this isn't exactly groundbreaking but it was a simple step that made a big difference to me. If you have any other suggestions for helping children to be familiar with the key concepts, please comment below!