The lower back, or lumbar spine, is a complex structure of vertebrae, disks, spinal cord, and nerves, it includes:
Five lumbar vertebrae, stacked one upon the other that connect the upper spine to the pelvis.
Six shock absorbers,or disks, which act as cushions and stabilizers to protect the lumbar vertebrae
Spinal cord and nerves, travelling through a central canal in the lumbar vertebrae, connecting your brain to the muscles of the legs
Small joints,to provide stability and allow for functional movement
Muscles and ligaments, provide strength, power, support and stability
The lower back protects the soft tissues of the nervous system and spinal cord, as well as adjacent organs of the pelvis and abdomen.
When standing the lower back holds most of the weight of the body; when bending, extending or rotating at the waist the lower back is involved in the movement.

Acute back pain is diagnosed if the condition has been present for a day to weeks. Chronic back pain lasts longer than 3 months.
The most common causes of low back pain are frequently a combination of factors that increase the likelihood of injury or disease. These may include:
normal aging (wear and tear), osteoporosis/fractures, a protruding disk, poor conditioning of the back muscles, overuse or improper use of the back, obesity, smoking.

EMERGENCY:
If you also have lost bladder or bowel control, call your doctor or be seen in an Accident and Emergency hospital right away.

How low back pain can be prevented:
Aging decreases bone mass, strength and flexibility, and cannot be prevented. But its effects on the body can be better controlled with:
• regular appropriate exercises to keep the muscles that support back strong and flexible
• proper lifting and moving techniques
• maintaining a correct posture when standing and sitting
• maintaining proper body weight -- being over weight puts strain on back muscles
• avoiding smoking
Low back pain can often be treated, but requires a professional examination . The following may be used (and often in combination) for the treatment of low back pain:
• resting the back
• medications to relieve pain and muscle spasm
• local heat applications
• massage
• reconditioning exercises to strengthen the low back and abdominal muscles
• weight loss
• quitting smoking
• a rehabilitation program to increase muscle strength
• light physical activity
• surgery
DO NOT IGNORE THE PAIN! It is there for a reason — the body's way of telling you something is wrong. It may sound obvious, but the first step is to stop doing whatever started the pain attack in the first place. Stop what you are doing, and ease yourself gently into a more comfortable position.

Exercises increase ability to be physically mobile, along with strengthening the muscles, and improving disks' stability.
A day of rest in the early stages may profit by lessening the pain initially by inactivity.

Physiotherapy: a physiotherapist can select from a wide range of treatment options to help relieve pain restore normal movement and strength which will change to suit your improving condition

Herbal Medicine: Chronic pain often creates other problems besides the pain itself. These may include: tension, spasm, insomnia, and depression. One herbal combination may include equal parts of willow bark (for pain), cramp bark (for spasm), valerian (a sedative), and St. Johns wort (an antidepressant). 

Osteopathy: Osteopaths use manipulation and specific thrusts to restore mobility to the musculoskeletal structure of the body. Diagnostic techniques are also similar to those of physiotherapy. Methods for treating acute or chronic back pain depend on the cause of the problem, and range from gentle massage to ease muscle tension, to pressure and stretching techniques to restore mobility to the joints. Several studies have shown that osteopathy can aid in the recovery from lower back pain.

Acupuncture: It has a wide variety of medical uses and can be especially helpful in dealing with musculoskeletal problems, such as arthritic symptoms, neck, back and joint pain. 
The pain relief comes quickly and is often long lasting; acupuncture combines well with osteopathy or physiotherapy