1. Start by standing with your feet shoulder-width apart and your knees slightly bent.
2. Step forward with your right foot and then bring your left foot to meet it.
3. As you do this, twist your torso to the right and raise your right arm up.
4. Then, step back with your left foot and bring your right foot to meet it.
5. As you do this, twist your torso to the left and raise your left arm up.
6. Repeat this basic step pattern, alternating between stepping forward with your right foot and then your left foot.
7. As you get more comfortable with the basic step pattern, you can start to add in some more complex movements.
8. For example, you can try jumping in between steps, or you can add in some arm swings.
9. You can also experiment with different tempos and rhythms.
Here is a video of Aiden Davis' performance at the Britain's Got Talent final. The move you are asking about starts at 1:48 and ends at 1:50.
Watch the video: https://www.youtube.com/watch?v=qK6_gF4j520