what is "contact"?

​What is “contact”? More specifically, what is GOOD contact?
Contact can be defined as, “the soft tension between the rider’s hand that creates a light but steady seat of the bit in the horse’s mouth”. Good contact has the potential to be the most intimate form of conversation between a horse and rider and is something that should never be taken for granted.
“The rider should have the feeling that he is connected to the horse’s mouth by means of an elastic ribbon” “… this elastic connection can be brought about only by the supple flexion of the horse’s jaw combined with the sensitive and light touch of the rider’s hands”- Podhajsky, The Complete training of Horse and Rider.
In my opinion, there are three key factors that play into creating a truly good contact. Education, Relaxation and Balance.
The young horse being started under saddle first learn to simply accept the connection to the rider’s hands. At this stage the rider should only be meeting the horse with a light contact that does not hinder their natural up/open head carriage in any way. Once the horse has learned to accept the bit you can start to educate the mouth with a series of in hand exercises that will start to mobilize the horse’s jaw.
“Correct contact is always connected with a good mouth. The mouth is called good or lively if it appears not only freshly reddened by freely circulating blood but it is also kept moist by the generous secretion of saliva as a result of chewing on the bit” Steinbrecht, The Gymnasium of the Horse.
Balance and relaxation go hand in hand, you cannot have one without the other and you cannot have a soft contact if you do not have both. A nervous or tense horse will often either lock their jaw or chew excessively, neither of which will create a good connection. A horse who is tense in the mouth will be restricted in the rest of their body. A horse who is out of balance will always carry tension in their body.
“A perfect contact is possible only when the horse is in absolute balance, carries himself, and does not seek support from the reins. It may be then said that the horse is “on the bit” – Podhasky, The Complete training of Horse and Rider.
Education puts the horse in balance and allows them to understand what is being asked of them which nurtures relaxation in mind and body. “Correct head carriage and lifting of the forehand are not major goals of dressage but rather accompaniments and consequences of proper work.” Waldemar Seunig, Horsemanship
I challenge you to ask yourself, what does good contact mean to you? How would you describe the feeling?