Shiatsu is very difficult to describe, but once you've experienced a Shiatsu treatment, you'll know exactly what it is and how wonderful it feels. If I had to give a nice succinct description of what shiatsu is, I would say it is acupressure massage that realigns your body and your meridians at the same time.
Shiatsu was developed in Japan and it grew out of an older system of massage called Anma into which was incorporated elements of Chinese Medicine (the meridians system and the acu-points). There are several styles of shiatsu, each with it's own emphasis and focus. The system I practice is often called Zen Shiatsu which focusses on treating the meridian system of the body. In essence, Zen Shiatsu brings the body back into a balanced state by finding the most Yin and most Yang meridians in the body and balancing them - taking what is most out of harmony and helping it come to equilibrium. Some people have described Zen Shiatsu to be like having yoga done to them because it incorporates some gentle assisted stretches to activate the meridians during the treatment. Other people liken it to acupuncture without the needles because of the use of acu points to stimulate the Qi.
That's all pretty heady stuff, but when you actually have a shiatsu you don't need to worry about any of that, instead, you can look forward to a wonderfully relaxing treatment that combines massage, stretching and acupressure to leave you feeling relaxed, refreshed and balanced!