These reiki symbols are meant to channel reiki in different ways, and to be used as focal points for the practitioner to use in order to focus their consciousness towards a specific goal when working with reiki. There are many different variations of these symbols many of them claiming to be the authentic original, but all of the many variations all seem to be effective when being used to work with reiki. These symbols will usually be drawn three times in the air, or on another surface, while the name is repeated out loud, or in the head of the practitioner. These symbols are also said to be able to be carved, or painted on objects, and then charged in order to be used as healing tailsmans, and other objects, though this is a non-traditional practice. It is important to visualize the symbols powerfully while using them, so that they can be active and take on their power in your life. You are also able to visualize any of these symbols on the backs of your hands in order for them in order for them to begin channeling their intention, and purpose into your palm so that you will be able to use it in your reiki sessions.
One insightful understanding that I have heard for the reiki symbols is that Master Dr.Mikao Usui intended the symbols to act like training wheels for focusing your consciousness in different ways to manifest reiki. After you could focus in a specific way to get reiki to do something they were said to be discarded. This would be because they would not be needed anymore, and all you would need to do is simply invoke that focus again, and you would be able to manifest reiki to do that specific thing. This was definitely a very interesting understanding though I have no evidence of its authenticity, it is still a very good understanding to have.
You must be attuned to the symbols in some way for them to work properly for you. Reiki can be harnessed without the use of these symbols though it is definitely a good way to focus and enhance the power of this energy.
All of the reiki symbols except for the Cho Ku Rei will usually also be used in a sort of pattern usually referred to as a reiki sandwich. This is where you first use, and project the Cho Ku Rei symbol, then any other form of reiki symbol you would like, then finally you use and project another Cho Ku Rei symbol. This will allow you to draw in stronger reiki energy from the combination of the Reiki symbols being worked with together.
Cho Ku Rei:
The Cho Ku Rei symbol is the reiki power symbol it invokes the energy of reiki in a very powerful manor. The Cho Ku Rei symbol can be used alone, or can be used with all the other symbols in order to bring Reiki energy into them.
Sei He Ki:
The Sei He Ki symbol is the mental and emotional reiki symbol. This symbol help heals the mind, logically, and emotionally.
Hon Sha Ze Sho Nen:
The Hon Sha Ze Sho Nen symbol is the distance reiki healing symbol, and it allows you to send reiki at a distance. Not only that but it is said to also transcend time, and space, and because of this reiki can be send long distances, or places in the future, or the past in order to heal situations.
Dai Ko Myo:
The Dai Ko Myo is the master symbol and it is used in the attunement process to allow the practitioner to begin attuning people themselves.
There are also many non-traditional Reiki symbols, which I will not talk about all of them here, but I did want to hit the more popular ones.
Tibetan fire serpent:
The Tibetan fire serpent is used to during an attunement to awaken kundalini energy.
Tibetan Dai Ko Myo:
The Tibetan Dai Ko Myo is substituted for the traditional Dai Ko Myo. Some practitioners prefer to use it.
The Raku symbol is used to break the connection between student, and teacher at the end of an attunement. Also sometimes used to cut off the flow of reiki energy.