Muscle memory, or repeating something so many times you can do it without conscious thought. It's really the root of all physical training, and really it's something we utilize in all aspects of our daily lives.

If you're a full time kilt wearer, think of this example. Do you still consciously sweep your pleats before sitting, or is it something you do automatically, without thinking about it? Do you ever catch yourself "sweeping the pleats" even when you're in pants? If so, that's muscle memory. It's something you've done so many times you're body learned that when you start to sit, you have to grab the back of your legs and sweep down as part of the process.

Alan was mentioning this as part of his Highland Athletics training, working on technique and doing it over and over again until it's automatic. Many of the events require you to perform dozens of separate actions in exactly the right sequence, and at exactly the right time, for just the right degree of force in order to give you a successful throw. If you don't practice you have to think about each one of those separate elements and frankly the human brain just doesn't work that fast.
Fortunately, as you start working the various elements together you build muscle memory and your body learns to perform some of those tasks on auto pilot whenever you find yourself in a similar situation.