A "lesson" is defined by Webster as: "A piece of instruction or teaching". In a "Group Ballroom Dance Lesson", this means: "do this, do that, in this sequence". The student is told what to do and goes through the repetition of the movement until the sequence is learned.
"Training" is defined by Webster as: "The act, process, or method of one who trains". In "Private Ballroom Dance Training" it means: "This is what you are trying to do, this is how it is done, this is why we do it in this particular way and this is how it feels. The dancer understands what is to be accomplished, how it is to be done, why it is done this way, and the feeling that is to be achieved.
Group Ballroom Dance Lessons are intended to expose a student to a series of movements for a specific dance style. Foot patterns are taught to allow the student to move through a particular sequence. Both sides of the partnership are taught the same sequence. The goal of the lesson is for the two partners to be able to navigate through the movement sequence taught. Partnership and lead and follow are usually secondary considerations.
Private Ballroom Dance Training is intended to teach students the technical intricacies of Ballroom Dancing. This means, lead and follow, footwork, timing, partnership, connection (physical and logical), shape, power, exchange of power, feeling, momentum, partnership balance, leg swing, partnership center, controlling movement, the unique character of each dance, etc. These technical intricacies require hands on with the student. All of the above develops that unique "four-legged feeling" (a feeling that can only be achieved with a partner). Ultimately, the partnership becomes a single two-headed four-legged animal (entity).
In all fairness, Group Ballroom Dance Lessons are not intended to teach the technical intricacies of Ballroom Dancing. The instructor actually needs to have his or her hands on the student so the student can experience how it feels and what it should be like. This isn't normally possible from a Group Class perspective because of the number of students in the class. "Dancing is actually what happens between the steps". You learn "steps" in Group Classes and you learn how to "dance" them in Private Training.
Beware, some instructors teach Private Lessons the same way they teach Group Lessons. This is not training. This is just a one-on-one Group Lesson. Find an instructor that has the ability to teach the technical intricacies of Ballroom Dancing. I tell my students: "Learn the patterns in Group Classes and then learn how to dance them in your Private Training". If possible, don't waste your time and money learning patterns in your Private Training.
There is so much more to Ballroom Dancing than just walking though foot patterns as you do in Group Classes. Without the technical intricacies taught in Private Training you will become what I call a "pattern Dancer". A "pattern Dancer" is someone that has no training beyond Group Classes. This results in their Ballroom Dancing being just linking together a sequence of patterns. In this environment, the patterns will feel the same in all of the dances instead of having a different feeling in each dance type. The dancer never gets to the stage where he/she experiences that unique "four-legged feeling".
It is very important for the lady to become a trained dancer. The man is in a little better position because he leads. He has the choice of what to lead so he will not lead anything he doesn't know. The lady, on the other hand, doesn't know what will be lead. It may be an element or pattern that she has not seen or experienced. If the lady is a "trained dancer" she will have a better chance of following the lead because she knows how the lead works and how to respond to it without knowing the specific element or pattern. Being a "trained dancer", puts the lady in a better position when dancing with a variety of men that have varying skill levels. Her training will allow her to dance with dancers of any level.
The goal of every Ballroom Dancer should be to become a "trained Dancer". As a "trained Dancer", you will understand the technical aspects of how to become a two-headed four-legged animal (entity), how it moves and more importantly how it feels. The goal is for the two dancers to not know where they end and their partners begins and to experience the feeling of being ONE on the dance floor.