Chiropractic is a non surgical, drug-free approach to increasing function within your the body, resulting in increased health and wellbeing
The body is controlled by the nervous system, the nerves that exit at each level of the spine have very specific jobs, they control a range of functions, including skin sensation, organ function and muscle tone and strength. When there is a dysfunction/loss of motion which can be caused by trauma e.g. bumps, falls, surgery etc then the nervous system is usually affected, which can then result in an inability to heal correctly. Symptoms usually indicates there is a dysfunction of the nervous system, see some of them below:
Humans: 
- Headaches
- Back pain 
- Sciatica 
- Poor posture 
- Inability to relax 
- Sports injuries 
- Neck pain 
Dogs: 
- 'Puppy sitting'/altered sitting
- Discomfort when being touched or moving
- Hesitancy when climbing stairs or jumping 
- Difficulty when getting up after lying down
- Favouring to lie on one side more than the other
- Change in behaviour
- Change in gait or lameness
- Licking or chewing paws 
- Decrease in performance
Horses:
- Resistance to being mounted/ridden
- Altered performance 
- Pain or stiffness when being touched or moved 
- Lameness, altered gait or shortened stride
- Resistance to picking up feet
- Changes in posture
- Bucking or rearing 
- Difficulty or inability to taking a lead
- Pinning ears back, biting or snapping
- Difficulty flexing at poll
Chiropractors use adjustments, which is the application of a very precise force to a specific area to correct dysfunction/loss of motion within a joint, resulting in normal nerve transmission, which allows the body to heal correctly.