This is Gwang Gae hyung, the first form for advancement to the higher dan levels. It is named after the king of the Korguryo dynasty who recovered all the lost territories including Manchuria. It is a wide ranging form illustrated by the spread out expanse of the movements, like the vastness of his empire.
It also begins in a unique way with the "hands of heaven:
"This form begins with a movement called Heaven Hands. Legend has it that King Kwang Gae stood upon a hill and gazed through his hands towards heaven, asking the gods for a quick and successful battle, When the enemy armies came over the horizon the king thrust his hands apart to signal the start of the battle."
[NB: video credit Chloe Orsag]
This form uses slow and fast moves to emphasize the ki in breathing with striking, highlighting the power created from the 3 internal ways of force.
As a reminder, there are three cardinal ways to create power: translational (moving forward in the x coordinate), rotational (around the y coordinate), and vertically (dropping down in the z coordinate).
In addition there are three additional internal ways of generating power. First there is a coiling of the body like a spring loading the muscles actively and then passively allowing them to unravel like a loaded spring. Next the breath is used to maximally contract the whole body at the point of impact, Finally, the body connects through the ground, channeling through the conduit of the body to the point of impact. In this way, the entire earth is used to connect to the target.
Using these external and internal moves we amplify the power and speed of any technique. We become greater than the sum of our parts.
Here is a spliced version showing the form from the front and back [NB: video credit to Chloe Orsag]
Practice this form slowly and then with strong breath control. Pay particular attention to stance changes initiated by the lifting of the front foot into the new stance. Watch the form in different ways and try to imagine doing the form in your imagination. See the room rotate as you walk through the pattern in your mind. It is a great way to solidly the form and reduce "form salad" where the form becomes mixed up with moves of other forms. It will clarify the form in your mind.