In a nutshell, Reiki is energy. It is the universal life force that surrounds and connects everything. It can heal on all levels of being; physical, emotional, mental and spiritual.
As a Healing modality, Reiki is a channeling of this energy from Spirit/Universe/God through the Practitioner to the Receiver, which balances and restores the Receivers physical and ethereal bodies. In the process, the Practitioner also receives the healing benefits of a session.
Reiki is guided by Spirit/Universe/God to automatically go where it is needed and always works for the highest good of all involved in the Healing. Reiki can do no harm, the worst that can happen is that the Receiver refuses the energy, either consciously or subconsciously.
Reiki can do no harm, it can only be used for the highest good. There are no contraindications with Reiki. I have heard many myths about Reiki: do not use during pregnancy, do not use on broken bones; do no use on amputations...
Describing Reiki to someone who has never experienced it is like trying to describe colors to a blind person; you just have to experience it.
What kinds of animals do you treat?I haven't found an animal that I couldn't treat. A few have refused treatment for their own reasons, but Reiki is appropriate for all living things (including plants!).
I have treated cats, dogs, rodents of every variety, rabbits, guinea pigs, chinchillas, ferrets, reptiles, amphibians, fish, arachnids and insects, birds of all sizes, tigers, lions, leopards, wolves, foxes, bears, horses, cows, etcetera ad infinitum.