Reiki is a form of energy work that is extremely useful in healing work. There are many explanations for it....I encourage you to wander these pages and find the explanation that sings for you.
For myself, the origins of Reiki are less important than what it does, and how it can be used. It is a healing modality, but I have found, from my experience, that healing may be a (very desireable) side effect. My personal belief is that it links up with the "spirit template" of an individual, and, through clearing the channels between the realms, brings the forms of being closer into agreement. This is how health is returned to the physical....it helps the body help itself.
Reiki seems to be moderately sentient. It likes to help things work better, to help things get in line with that personal template.
It will react, quite forcibly if need be, to obstructions and interference with the expression of the template.
This makes it a wonderful tool in clearing attachments, and in combating manipulation. It will also not allow itself to be used to harm others.
Reiki is NOT for everyone, however. Some people do seem to have a negative reaction to Reiki, and this should always be respected.
Some people find the energy unpalpatable, and it can interfere with some energy systems. I do not know why this is, but it is something to be aware of.
Enjoy your wanderings among these pages. I have lots of my own personal notes scattered about, and will have a lot of information on practical uses. I even have among these pages an experiment of mine....the on-line attunement.
Basic Reiki (Eyovah) | Advanced Reiki (Eyovah) | Reiki for the Magical Practitioner
Reiki Classes (Eyovah) | Online Attunement | Reiki for Otherkin (Crisses) | Tapestry of Worlds Attunement