Ten I, Ten Tai and Ten Gi are the three basic components - it is how Wado operates.
Together they are called San Mi Ittai
In fact, every movement should use all three components. It may occur that only two out of three is used, but the ideal is to use all three of them, this is called San Mi Ittai.
Ten I means to move somewhere else. If you move far away from the opponent, of course you are safe. However, the opponent is too. Hence, move to a position that you are safe, but the opponent is not.
The location you are now, is where the impact is going to take place, so it is not the most ideal place to be. Ten I reduces the chance of receiving the full impact.
Furthermore, Ten I is a method to give your technique more speed and power.
Ten Tai is the second component which allows the attack to pass your body. It therefore has an avoiding function while at the same time creates more sharpness in your movement.
You need to use your body by i.e. twisting, shifting, dropping or rising sharply.
Use Ten I and Ten Tai to increase the power of Ten Gi, which simply means to execute a technique. Hence, after tactically moving to another position, you have to use the whole body to punch, kick, throw or control the opponent for example.