Reiki is the power to heal using "universal life force." Reiki itself is a system of natural healing coming to the west from Japan. A trained practitioner of Reiki healing has the ability to channel pure life force—what is known as ki, chi, or prana—and gently allow the recipient to absorb this life force. The recipient's own body can use the energy to heal, gently removing any blocks to health and increasing the flow of life force to areas that are ill or injured. Reiki also works on the energy bodies. Healing can occur on an emotional, mental, or spiritual level. Reiki differs from other forms of energy healing, because the recipient is said to be in charge of the transfer of energy. The recipient's "higher self" or "body wisdom" controls the flow, preventing any overload from too much energy. The Reiki practitioner is like a straw, the recipient sucks energy through the straw, and just like having a drink, when you've had enough, you stop drinking. The recipient cannot "choke" or overload on the healing energy.
As a practicing witch, I use healing magick in my life all the time. I was interested in learning how Reiki and magick were the same and how they were different. Although there are many traditions and teachings of magick, anyone can learn to use it. With some very basic knowledge, or even by closely following a spell recipe book, you can have successful results working magick without a lot of training. Magick is a method of speaking your intentions to the universe, and by using the symbolic language of ritual, you can speak your intention very easily. Tried and true ritualists know magical theory well enough to design their own rituals and spells, but anybody can learn a few basic techniques. Traditional spells become traditional because they work for a variety of people and get recorded in someone's spell book.
To practice Reiki, technically you must be initiated into the tradition. To do this, you must receive what Reiki Masters call an attunement (so called because your body is attuned to the natural flow of universal life force energy) through a ritual and variety of symbols. There are a variety of healing energy techniques that are similar to Reiki, but without the attunement, you are not practicing Reiki. The benefit of doing Reiki healing specifically is all the safeguards that come with the system. Not only will you never overload the recipient, but you cannot take on the illness of the recipient. The flow of energy is one way. Other forms of energy healing do not have these built-in benefits.
I know quite a few witches who get initiated into Reiki to supplement their magical energy. These witches use Reiki not just for healing, but also for many purposes. They use Reiki energy to charge candle spells, to consecrate herbal potions, and to cast the magick circle. The Reiki energy will flow wherever it's needed, not just into the body of one who is ill.
I've also found those who are versed in magick, but not initiated into Reiki, using the symbols associated with Reiki in magick. Originally the symbols were kept secret from the uninitiated. They were passed on and memorized, with few written copies preserved. Later, when Reiki became more mainstream, the symbols appeared in books and online websites. Now anybody can find them.
Although these symbols were kept secret to prevent people from using them without an attunement into Reiki, some believe they were kept secret so Reiki teachers could charge huge amounts of money to reveal the secret symbols in class. Lore about the danger of using them when you are not attuned to Reiki grew, and tales of how the Reiki symbols were misused in Egypt or Atlantis became a part of the teachings. Personally, I think they can do no harm. They convey healing energy that is guided by the higher self of the recipient. I think the danger is in thinking if you know the symbols, you have been attuned to Reiki, and have all the safe guards to do healing work with others. Someone using the symbols without an attunement may mistakenly use their own personal energy to heal, and become sick, taking on the illness of another. Or they might overload the recipient with too much energy. That's the only danger.
The benefits of using the symbols, even without having an attunement, can be great. I've given clients symbols written on paper to meditate on after a healing session. The names of the symbols can be used like mantras, to evoke their healing power personally into you. I even know someone who, before coming to a workshop, read my book, Magick of Reiki and found the symbol Cho Ku Ret from the Seichim Reiki traditions, which is used to heal inanimate objects. Her car broke down and she used the symbol on it, drawing it and chanting its name. Her car started back up again and she got to my workshop on time. I found that quite amazing.
I think chanting the names of the Reiki symbols in meditation is one of the easiest and safest ways to work with them if you are not attuned. Different teachers pronounce them slightly differently, so do your best and see what effect each has on you.
Explore working with Reiki through chanting. If you find the energy it evokes speaks to you, explore learning more about Reiki, researching the symbols, and even taking a class with a certified Reiki teacher to become attuned to it yourself.