It's applied so it indicates the direction you want the horse to go. And it is applied methodically and consistently. That's not the same as forcefully or insistently or repeatedly. A lot of people use swear pressures instead of aids. Instead of touching the horse with a whip or even just pointing it at him the right way, they slap him with it.
Aids are horse logical.
The horse reacts to that pressure or aid in a predictable way that is just natural or instinctive for a horse. For example, if you start approaching a horse from behind, he will turn his head one way or the other to see what's coming. If you're a little to his left, he'll turn his head to the left so he can watch you coming. If you're a little to his right, he'll turn his head to his right. If you're coming too fast or he's a spooky kind of horse, he may move off and ask questions later.