The technical aspects of Ballroom dancing are the building blocks that develop the feeling of each dance and creates the two-headed four-legged animal. It is what transforms mechanical geometric patterns into dancing. The technical aspects generate the unique feeling (character) of each dance. It is what makes a Waltz look and feel different from a Foxtrot, from a Tango, from a Rumba, etc. Otherwise all of the different dances look and feel the same. The difference between being a "Ballroom Dancer" and being a "Trained Ballroom Dancer" are the technical aspects of movement, partnership, music and feeling.
The one-headed two-legged animal (person) moves, acts and feels quite differently than a two-headed four-legged animal (partnership). Add to this the unique character of each ballroom dance and the movements and feelings get even more complicated. The goal of Ballroom partnership dancing is to develop the unique four-legged feelings that cannot be created in any other manner. The two two-legged animals disappear and a totally new single four-legged animal is born.
The technical aspects create precise four-legged movements and feelings. It is involved in all areas of the dancing two-headed four-legged animal. The areas I am talking about are Power, Movement, Control, Partnership, Feeling, Music, etc. What specifically are the technical aspects of Ballroom partnership dancing?
Let's talk about "Directional Changes" mentioned above. On the surface it seems simple enough, we don't even have to think about it, simply stop and go another direction. It would be simple if the dancer we are talking about is a two-legged animal, but it is more complicated when the dancer is a four-legged animal. Let's have the dancers execute a Slow Waltz "Open Left Turn" element (turning left 120 degrees). The leader moves forward, turns 120 degrees to the left, and then moves backwards. The follower moves backwards, turns 120 degrees to the left, and then moves forward. The follower is on the inside of the turn, thus moving a shorter distance than the leader on the outside of the turn moving a greater distance. Trying to figure this out in your head makes your brain hurt. What if the dancers had a common point in the partnership that both dancers could use as a reference point for their movement? This would simplify the geometry of the four-legged "Open Left Turn". That common point is the center of the partnership. The solution is to become four-legged. Four-leggedness has to be converted from a physical action to a feeling. The feeling of being four-legged has to become who you are as a Ballroom Dancer. Ultimately, the dancer wants to move by "feeling" not by the "thought" of mechanical actions.
The examples above are hard to understand from just the written text. The examples are actually feelings not mechanical actions. Dancers tend to interpret the examples as two-legged actions when in fact they are four-legged feelings. The four-legged dancer has a whole new different set of feelings. The goal is to combine the feelings of each dancer into an entirely new single feeling of the two-headed four-legged animal.
The lead and follow in ballroom dancing is composed of all of the technical aspects. There is no single "Lead" component. The technical aspects are also what allows the lady to move naturally in the partnership. Dancing is what happens between the steps. The four-legged feelings are created as a result of the technical aspects. The technical aspects of Ballroom dancing evolve gradually over time throughout your dancing career. There is no one defining moment where you suddenly have it. The technical aspects have been evolving since the beginning of Ballroom Dancing and continue to evolve to this very day.
Typically, geometric foot patterns are taught in group classes. It is hard to teach the technical aspects in a group class environment. The instructor requires a hands-on situation to be able to effectively teach the feelings that the technical aspects develop in the two-headed four-legged animal. The technical aspect of Ballroom Dancing is what will improve your dancing (not more patterns). As you can see from the above descriptions, you will not be able to pick these up from video tapes or group classes. They are not mechanics or geometry. They are feelings. Private (hands-on) lessons are the most effective way to learn the technical aspects that create the "feelings".