An imbalance is any significant difference between the two sides. Learn to name the ones in front of you and the plan stops being a matter of taste, because the board tells you what it wants. This course works through them one at a time, then through the pieces, the psychology, and the structures they live in, ending each stretch with tests labeled by rating.
Every lesson gives you a position to look at, a short read, and a set of exercises you answer on the board itself. Some ask which piece to move, some ask which piece must stay where it is, some ask where a piece belongs, and some ask you to play the move. Finish a lesson and it turns green, which opens the next one.