It is written in the devanagri text/font, which makes it appear as a symbol.
Each chakra is fed by prana, through a number of nadis specific to that chakra.
There is a sound vibration, mantra, related to the flow of prana in each nadi and often this is written on the corresponding 'petal' in a chakra yantra, in devanagri.
These mantras are said to be imperishable sound ... akshara.
As the prana flows through the nadis, it collides in one point, as one sound, one explosive mantra, in the centre of the chakra. This sound, or mantra, is the bija mantra.
Here is a picture of each of the chakra bija mantras - you can see them individually, related in the chakra yantras, below.
Mooladhara chakra has four nadis feeding prana into it (from the upward point of each petal, down to the absolute centre) and the bija mantra which results from these four sounds combining, is LAM, pronounced lum.
Swadhistana chakra has six nadis feeding prana into it and the bija mantra which results from these six sounds combining, is VAM, pronounced vum.
Manipura chakra has eight nadis feeding prana into it and the bija mantra which results from these eight sounds combining, is RAM, pronounced rum.
Anahata chakra has twelve nadis feeding prana into it and the bija mantra which results from these twelve sounds combining, is YAM, pronounced yum.
Vishuddhi chakra has sixteen nadis feeding prana into it and the bija mantra which results from these sixteen sounds combining, is HAM, pronounced hum.
Ajna chakra has two nadis feeding prana into it and the bija mantra which results from these two sounds combining, is AUM, pronounced om.
To chant these syllables of sound is to activate potentiality in that chakra.
Chanting lum awakens deeper personal security, lessening neediness and increasing surrender to the process of divinity.
Chanting vum awakens joy, lessening the desire to gratify, increasing detachment.
Chanting rum awakens motivation, lessening the need to be helped, increasing will-power.
Chanting yum awakens love, softening the critic within, increasing compassion for one and all without reasoning.
Chanting hum awakens inspiration, lessening resistance, increasing purity and sweetness.
Chanting aum awakens wisdom, lessening conditioning, increasing intuition.
Chant bijas for releasing the old and the stuck ... and bringing in the fruit of surrender, detachment, willpower, compassion, sweetness and intuition.
Bija Mantra Meditation
Note, this meditation is releasing old blocks, which must pass through your mind and nervous system. So go carefully. Don't release too much, too soon, because you still have daily life to get on with. Go softly forward.
Practice seated, comfortable, eyes closed. Awareness taken within, internalised.
Focus awareness into mooladhara chakra inhaling slowly into mooladhara so you can concentrate on feeling the vortex of prana there, with your imagination.
After the breath is finally inhaled, begin exhaling, chanting aloud "lum lum lum lum lum lum lum . . ." awareness still focused into mooladhara chakra- exhaling slowly, dont push the breath out quickly. Make it measured.
Try to focus INSIDE and not on, each chakra.
When that breath is completed in mooladhara, you then continue this process with each of the other chakras up to ajna, then from ajna return down to mooladhara, again.
When you are more familiar with the practice and have more time, you can do more than one breath to each chakra.
Too many rounds causes to much activation, which means your nervous system may get strained.
1-5 rounds causes plenty of inner change, safely, and with no strain to the nervous system if practiced on a regular basis.
Focus awareness into the absolute centre of mooladhara chakra and inhaling mentally chant "lum lum lum lum lum lum lum . . ." continuously until the breath is finally inhaled. Then mentally fire the mantra lum into the centre of mooladhara as many times and as strongly as you can, while exhaling slowly.
Continue this process with each of the other chakras up to ajna, then from ajna return down to mooladhara, again.
When you are more familiar with the practice After one round per chakra - and if you have enough time, you can do more than one breath to each chakra.
The same precautions for beginners applies here, too many rounds causes to much activation, which means your nervous system may get strained.
3-7 rounds causes plenty of inner change, safely, if practiced on a regular basis.
Hari Om Tat Sat.