As I have mentioned in the past, I view the dance as a conversation between a leader and a follower.
The means of communication in this conversation is the concept of connection.
It is always present in our dancing, regardless of skill.
In Dance: a Fundamental Philosophy, I have used the metaphor of language to describe connection.
Once the leader and the follower establish a basic connection, the leader manipulates the connection to give a lead, and the follower attempts to return to that connection to follow.
For example, in a side pass, the leader steps backwards, creating a tensile force in the connection. The follower feels a stretch and moves forward to relieve that tension. She continues the motion until she receives another lead. The leader will turn around as she passes, and the follower will feel the lateral tension, and turn around to face her lead again even as she continues her original motion. The follower continues moving, now in the backward direction until the leader leads her to stop by remaining in place and gradually producing the same tension that he led the movement with. The follower feels a tension theoretically identical to the initial lead, and relieves that by remaining in place as well.
The process by which all this communication occurs is complex and development of good connection requires many related concepts to be practiced.
The first concept that should be understood is center- possibly the most important concept of connection. The significance of center is that all contact-led movement should be theoretically led from the center. A better center leads to more stability, stronger connection, and clearer communication. An analogy I could give is that a ball of yarn is much easier to manipulate than when it is unraveled. The idea of a good center is to consolidate all of your weight and energy as small as possible into an area that can be connected with your partner. The general area is usually always somewhere in the torso, but specific locations are different for leaders and followers and for the style being danced. The location can be very specific for skilled dancers (for example, the powerhouse, the solar plexus, or the sternum, and the precise positioning of the center with respect to the legs or the head).
A few good methods to maintain a good center are moving your torso before moving your legs, and always keeping your center over your legs.
Now I have mentioned that we lead and follow with our centers, but how do we connect them to each other? Imagine how limited our motion would be in Lindy Hop if we could only connect our centers through direct contact! However, we can dance in other positions through the concept of frame. The way the center of two dancers can connect is the concept of frame. Lindy Hop frame is rather difficult both to explain and to achieve. The idea of good frame, albeit vague, is to present the clearest physical connection between our centers. In Lindy Hop, we are often in open position, connected by our fingers, which is a great distance along the arm and the body to the chest. The general concept of frame is not too difficult to grasp- it's simply providing something tangible for your partner to work with when he or she contacts you. However, fine-tuning the frame to be comfortable and comfortable is another matter altogether.
Lindy Hop utilizes a dynamic frame, in which the frame is not rigid, but fluid and flexible. Therefore, movements are not instantaneous, but led and followed through cycles of stretch and release and/or compression and release. This results in a necessary pre-lead, which is one of the characteristics that make the dance swing as well as allowing Lindy Hoppers to spontaneously improvise moves and styling with unfamiliar partners.
Like a jet plane has a frame to absorb the thrust of the engine, a follower has a frame to absorb the lead. The leader has to also provide a frame as well for the follower to work against. As the movements end, the frame
Tension is a very closely related concept of frame. Tension refers to the amount of potential energy stored inside the frame, much like the amount of tension required to manipulate a spring. Variations in this tension help communicate certain things such as the distance to be traveled or the speed at which moves are to be executed.
Tension is a very defining aspect of individual dancers. While tension does vary in the course of a dance, there is a general characteristic tension that each dancer will tend to gravitate towards in certain styles and music. That general "default" tension is classified as heavy or light, depending on if more or less energy is required to maintain the neutral connection and initiate movement, respectively.
The advantage of heavy tension is the obvious presence of a connection to both parties. The leader has clear and positive control of his follower and the follower has a very secure lead. The dancing is generally smooth and comfortable, as most extraneous movement contributes an insignificant amount of energy to affect the connection. This can be achieved with relatively little skill level and is useful for teaching concepts such as stretch and compression, and sensing weight changes of your partner. However, heavy tension comes with the price of lower stamina, especially at higher tempos, due to the greater amount of "overhead" energy required to maintain connection as well as initiate movement.
The advantage of light tension is greater freedom, responsiveness, and flexibility. The follower has more freedom to express herself, and the leader can provide more subtlety in his dancing. However, lighter tension typically requires a great deal of refinement and skill to dance well in this manner. Response time is less, as well as the energy to maintain connection, allowing for dancing at a greater range of tempos with greater stamina.
There is no "wrong" tension besides one that your partner is not doing.
Once center, frame, and tension are in place, the lead manipulates the connection to cause movement. A smooth way of doing this is moving his center.