Chasing the tiger
Chasing the tiger is nothing more or less than letting your horse chase a plastic bag/piece of clothing or something else that you hold in your hand or have tied to a stick/whip/pole. A lot of traditional trainers also use sticks/whips with plastic tied to it, but then in order to let the horse flee away from it in order to make them run. You can compare it to the rope that is flung to the horse in a join-up, or even a lungeing-whip that is cracked in the air in order to 'scare' the horse so that he becomes faster. These training methods reinforce the horse that the human is the hunter and the horse is the prey, and therefore subordinate to the human.
We do it the other way round.
First you teach your horse through rewards that he can put his nose against a plastic bag that you're holding in front of him - and reward a lot for that! Then you just walk a step away from your horse and ask your horse if he wants to follow you and touch the bag again. Then slowly take longer distances, or let your horse touch the bag longer while walking, before you reward. If that's all okay, you can tie the bag on to the end of a whip and start running away from your horse, animating him into a trot or canter while holding the bag in front of him. When you tie the bag to a longer driving/lungeing whip, you can lunge your horse around you like this, let him do the more energetic moving while you're in a safe distance (and a bit less tired
The most important reason to do this, is that most horses just love it. They love the fact that they're the hunter instead of the hunted and that they can chase instead of be chased. Because for horses, chasing each other is very natural too, only a lot of horses never chase others because the others always chase them. So giving them the opportunity to change place really can give them a boost of self-confidence.
Chasing the tiger is also a very good way to conquer fears. Clickertrainers already know that targetting a scary object with the nose easily convinces horses that that object isn't that scary after all. Chasing is makes it even more harmless, as obviously the previous scary object is now running away, and therefore scared of the horse.
So let the horse be as wild as he wants to be with the bag (or other object) and reward him for that behavior. Touching the bag with the nose is very good, but stamping on it with a front foot is even better, as it means that your horse dares to come closer to it with his body.
Another reason why Chasing the Tiger is a great game, is that it teaches horses to move freely and at higher speeds eventually, even the more timid horses. It also offers a wonderful opportunity to 'make' horses more independent of you, especially those horses who don't play wild games on their own because they don't like to leave you.
The last reason is that lungeing in Chasing the Tiger-style, with the horse following the bag with his nose stretched out down and forwards, is a very good way to loosen the back. With horses who tend to lean a bit too much on the frontlegs when moving, you can also hold the whip with your targetbag more at knee-or breast-height.
Essentially you can play Chase the Tiger with anything: with wooden planks that you drag through the sand, or a jacket tied to a rope so that you can drag it behind you, or a tennis ball or piece of cotton tied to the end of the whip. Start easy, with an object that isn't that scary according to your horse, and gradually you can make the game more interesting by taking more scary materials (plastic, wild colors) and by asking your horse to follow it at higher speed. Experiment! And everybody with new ideas for this game, place them in this topic!
Follow a Tiger towards collection
For the Tiger-experienced horses, Chase the Tiger is also a very good way of introducing them to good self-carriage and collection, as Marleen shows in her video amongst others.
For stretching the neck/back, you can keep the Tiger really low on the ground so that the horse follows it in a forwards-downwards posture. However, when he gets better at that, you can also start lifting the tiger a bit at knee/breast height of your horse and instead of just pulling it away from him (which would stretch the neck out again), move it away and then a bit towards him and then away again in for example walk or trot. Most horses will respond to that by raising the front, lifting the neck while looking down (the ramener-pose) in order to kick the hell out of the tiger with the frontfeet - using natural collection exactly for what it was originally meant for in the wild.
That way you not only can let your horse experience that collection is fun (and useful ) too, but you can also get more jumpy, upwards movement that you can put on a cue during the CtT game, and then develop and refine further as haute ecole movements (Spanish trot, passage) and jumps (terre a terre, rear, courbette...? ). That way your horse introduces himself to higher collection that you can use in the focused work again, while even more important, he also learns that moving in such an extravagant, flashy, impressive way is fun.