Four categories of junbi.
Junbi seogi it self is the most basic junbi at the "MA" position. A position of solemnity and preparedness where our thoughts become unified to halt distraction, where standing inaction is action. Breathing, focus, mind ready because every success comes from the mind. At the beginning of Poomsae, Junbi seogi could be compared to a religious position, ready to take a journey of self discovery. At the end of Poomsae, jumbi seogi can again be compared to a religious position of self review, going back to the beginning, or "MA" position, to review what has happened, what I have experience, what were my actions, what flaws existed, and where in my mind did these flaws come from, and, finally, how can I improve to "cure" these flaws.
Tongmilgi junbi seogi. Tong means something round or circular in shape, like a rock, log, tube, football, etc. Miligi means to grasp and maintain a force against something, stabilizing it, like "pushing against" more than just pushing. This position is highly symbolic and maybe only slightly application oriented. It represents the part of the Yeokhak Theory (Science of Changing), specifically the circle or point, called "won" in Korean language, hence the hands grasping a circular object. The circle is representative for the heavens and/or sky.
Kyopson junbi seogi. Kyop means layered/stacked/piled/overlapped, son means hand. This position is also highly symbolic and maybe only slightly application oriented. It to is from Yeokhak Theory and specially represents a surface/base/plane/earth/a flat line or square, called "bang" in Korean language, hence the hands piling at the bottom of the danjun or abdomen, showing earth as the beginning of life.
This flat line or square represents earth.
Bojumok junbi seogi. Bo means augmented, jumok means "fist." As we stand in this Poom of bojumok junbi seogi with hands raised and centered in front of the chin, our arms make the shape of a triangle, or "gak" in Korean language. This to is from the Yeokhak Theory and means "human." Again, not much application, highly symbolic. The left hand is open and represents the plane of earth, the right hand is made into a fist and represents the circular shape of the heavens. The open left hand covers the closed right hand, but does not actually touch it. Combining of heaven and earth creates human. This is symbolized by "bojumok", the earth and heaven combining to create human through harmony of the universe and this returns humans back to Taegeuk.