What is Reiki?
As a Reiki practitioner since 2012, I get asked about Reiki a lot and I usually offer the questioner the opportunity to experience it themselves to define what Reiki is to them. I find that describing Reiki is much like trying to use words to explain what Love is, or trying to describe a sneeze to someone who has never sneezed before. Reiki, like love or sneezing, is totally natural and instinctive, its pleasant and healthy, but it is not easily described. Perhaps that is why not everyone has tried it yet!
For my experience of giving Reiki, I often encounter the feeling of the flow of Reiki as similar to sensing the temperature of water. Much like swimming in a heated pool allows you to 'feel' the warmer temperature of water coming directly from the heating system by swimming through and centering in on the warmest spots, I am sometimes (but not always) able to detect Reiki energy in areas where a recipient is accepting the flow.
Interestingly, in an instance when I am feeling very hot temperatures while working with a client, many times they will comment on how cold the same location feels to them! And the reverse can happen as well. Sometimes I feel nothing and the feedback is how hot a spot was. As I say, Reiki is a personal experience that feels differently, or is described differently, by many of the recipients. Further, on seperate days, sessions can feel very differently for the same person as well.
To assist your research into the subject, here are some websites on the topic: