To explain the concept of loops to my year 3 students I would begin by instructing one student to do a simple action, e.g. 'stand up'. Then I would say 'sit down'. Then I would repeat it again, 'Stand up. Sit down.' Repeat it again. When the student has repeated the process a couple of times I will say that it may have been a lot easier, and quicker if I had asked him/her to stand up and sit down four times.
I will explain to the students that a loop is used to help us save steps when programming. You can shorten directions by putting some steps in a loop.
We will then look at the Unplugged Activity of the dance steps and work through the process of identifying steps we could put into a loop.