There are techniques in Aikido and there are motions. Here I will set about showing the four basic motions for as they improve only then does technique improve or indeed manifest properly.
There is Taisabaki Motion. Tenkan Motion. Irimi Motion. Ikkyo Motion.
The first motion we shall address here is the motion of TAISABAKI. Basically, this is the motion of turning your body around to face the opposite direction. You can do this in two ways. Let's say you have your right foot forward, if you swing your back foot, (your left foot around in a clockwise motion), and then as it lands let your right foot swing round behind it, you will have completed a 180 degree turn and be facing the opposite direction. This is taisabake.
On the other hand, if you have your right foot forward and you pivot on it in an anticlockwise direction allowing your back foot (left foot) to swing round then you are doing another motion called TENKAN. The use depends solely on what angle of attack you are harmonizing with. That’s the physical aspect dealt with, so now let's ask the question why? WHAT'S ITS PURPOSE?
The purpose is to harmonize with the opponents motion, their motion contains both movement and energy complete with a mass called a body AND their space.
Ahhhh. Space. You are turning into their space. Remember, a person has a personal space and if we look at this two dimensionally, they have a circle around them, so with Taisabake you are turning into their circle. Why? Your aim in Aikido is to follow the principles of harmony and thus to BE WITH. You enter with the feeling of MEETING and WELCOMING. You enter with the intention to join and be with. You enter with non-resistance. You enter in this way so that you are in harmony with their energy, their motion, their body, their state of mind and you enter into the center of their circle to align yourself with their center hence you have spirit, mind and body in harmony. You do not enter in order to do a technique you enter in order to BE WITH.
This is a fundamental PRINCIPLE of Aikido Motion.
TO CO-EXIST IN HARMONY!