The discovery and use of adaptogens in modern science are relatively new versus the use of them in traditional herbal medicines such as Chinese and Ayurveda medicine for thousands of years.
Adaptogens, simply put:
Help the body balance out and reduce the internal physiological and psychological stress triggers.
Help to normalize physiology in response to change. For example, if your immune system is auto-immune (running too high) adaptogens will slow it down or if it’s too low they will pick it up. They are a two directional – normalizer and a modulator.
Adaptogens do not negatively affect the homeostasis of the body. They are innocuous and do not influence normal body functions more than required .
TCM (Traditional Chinese Medicine) views stress and our internal survival system as an ever-evolving balance in the body systems. Adaptogens maintain a balance between excess and deficiency of our physiological system (Yin / Yang Theory).
Being an adaptogen is only one aspect of the individual herb. Each herb has its own functions alongside being an adaptogen, for example:
Turmeric used as an adaptogen in Western and Eastern medicine
In Western medicine Turmeric will reduce the severity of your innate defense mechanisms by:
Controlling the immune system by controlling the liver and the way your nervous system responds to stress by reducing the severity of the stress trigger.
Reduces and controls inflammation.
Reduce blood lipids.
Lowers blood pressure.
Reduces platelet aggregation.
In Chinese medicine, turmeric (Yu Jin) has been used since the Tang dynasty (618-907) primarily for:
Blood and Qi circulation (reducing pain and inflammation from trauma, chest, menstrual and flank pain, increase healing).
Ease the mind (calm anxiety, heart palpitations and wandering thoughts).
Remove stagnation of undigested foods by increasing the release of bile.
Turmeric is a cooling herb, reducing heat toxicity in the blood.
Functions of other Adaptogen herbs
Tulsi (Holy Basil): Adaptogen, aphrodisiac and liver supporter, anti-oxidant, anti – anxiety.
Ashwagandha/Withania: Supports the parasympathetic nervous system, acetylcholinesterase inhibitor (sleep quality, digestion, detox short term memory, concentration, recovery, meditation), building up the chemical which has the opposite effect to stress. 
Schisandra: Antioxidant, protects the liver, tonifies the nervous system, commonly used in Chinese medicine to reduce anxiety, calm the mind, whilst still being able to increase endurance and energy and libido. 
Rhodiola (Hong Jing Tian): More sedative adaptogen, reduces the adrenal crash, reduces the effects of palpitations and anxiety often caused by excessive adrenal output. Rhodiola “enhances the transport of the serotonin precursors, tryptophan and 5-hydroxytryptophan (5HTP), into the brain. This promotes the secretion of beta-endorphins by the brain and thus promotes a feeling of mental ease and contentment.” 
The paradigm shift in thinking about health
Viewing the body as a microcosm of the macrocosm.
Adaptogens work with the individual bringing harmony to core physiological mechanisms, as opposed to be a symptomatic based treatment. They affect the individual in accordance to what the individual system is requiring. For example, the same herb (given in the same form) can have two different effects for two different people, depending on the individuals need of the plant. A person with fatigue due to adrenal burnout can take an adaptogen and it will increase their energy, a person with hyperactivity can take that same herb and it will subdue their energy.
Our understanding of the negative effects of using “straight jacket” type pharmaceutical approach is turning our exploration and practices in modern medicine to a holistic approach. Unifying the traditional application of herbs with modern pharmacopeia. Adaptogens are a ‘do no harm’ approach to healing.
When looking at the microcosm as a reflection of the macrocosm, immunity creates friction and differentiation (the continual flux of Yin and Yang). Adaptation creates unity (the source of Yang within Yin and Yin within Yang). Immunity is often generated by will and attack mechanisms; whereas, adaptation is often generated by love and cohesion. Immunity is about the polarized individual and adaptation is about unifying our community, our Biota – both are needed for harmony.
By using herbal anti-stress adaptogens we are increasing our core vitality and integrity beyond immunity, increasing our systemic resilience to stress and stressors, and amplifying our ability to accept, allow and adapt to stressors. This is key to returning, as vehicles of consciousness, to the inner/individual and outer/collective health that we all want for ourselves, and our loved ones, including this good Earth.