Acupuncture is a technique of inserting and manipulating fine filiform needles into specific points on the body with the aim of relieving pain and for therapeutic purposes. Note that these needles are much finer than the needles used for injections which clients will have experienced. 
Acupuncture treatment regulates the flow of Qi(Chi) and Blood, tonifying where there is deficiency, draining where there is excess, and promoting free flow where there is stagnation.
TCM treats the human body as a whole that involves several “systems of function” generally named after anatomical organs but not directly associated with them.
Disease is understood as a loss of balance of Yin, Yang, Qi and Blood. Treatment of disease is attempted by modifying the activity of one or more systems of function through the activity of needles, pressure, heat, etc. on sensitive parts of the body of small volume traditionally called “acupuncture points”.
Most of the main acupuncture points are found on the “twelve main meridians” and two of the “eight extra meridians” (Du Mai and Ren Mai) a total of “fourteen channels”. The first twelve channels correspond to systems of function: Lung, Large Intestine, Stomach, Spleen, Heart, Small Intestine, Bladder, Kidney, Pericardium, San Jiao (an intangible, also known as Triple Burner), Gall Bladder, and Liver. Other pathways include the Eight Extraordinary Pathways (Qi Jing Ba Mai). Ashi (tender) points are generally used for treatment of local pain.
Safety
Acupuncture needles penetrate the skin, many forms of acupuncture are invasive procedures, minor bleeding after removal of the needles, is seen in roughly 3% of patients; About 2% of patients experience minor bruising, which usually goes away after a few days; About 1% of patients have a conscious or unconscious fear of needles which can produce dizziness and other symptoms of anxiety.
What can acupuncture treat?
Below list of diseases and conditions can be treated by acupuncture safely, effectively which are recommended treatment with acupuncture by The World Health Organisation.
Psychological & Emotional Disorders
Addictions;
Anxiety;
Depression;
Insomnia;
Panic Attacks;
Stress
Skin Disorders
Acne;
Allergies;
Eczema;
Psoriasis;
Shingles
Respiratory Disorders
Asthma;
Bronchitis;
Catarrh;
Coughs & Colds
Eye, Nose & Ear Disorders
Conjunctivitis;
Rhinitis;
Hay Fever;
Tinnitus
Digestive Disorders
Colitis;
Constipation;
Diarrhoea;
Gum Disease;
IBS;
Haemorrhoids;
Heartburn;
Hiatus Hernia;
Ulcers
Musculo-skeletal Disorders
Arthritis;
Rheumatism;
Frozen Shoulder;
Muscular Pain;
Back Pain;
Repetitive Strain Injury;
Sciatica;
Tennis Elbow
Circulatory & Heart Disorders
Angina;
High Blood Pressure;
Palpitations;
Raynaulds Disease
Women’s Health
Menopausal Issues (hot flushes, night sweats);
Menstrual Issues (PMS, Pain, Irregularity);
Fibroids;
Polycystic Ovarian Disease;
Pregnancy;
Preparation for Birth
Miscellaneous Disorders
Cystitis;
Dizziness;
Headaches;
Migraines;
Fatigue;
Tiredness;
Infertility