Gam is the most important bija mantra and is part of the important Lord Ganesh mantra, Om Gam Ganapatey Namah.
Glaum on the other hand is more of a tantric bija mantra and is used in special instances which helps to remove major obstacles so that we can proceed with our usual Ganesh sadhana (prayers) using the Gam mantra.
Lord Ganesh energy is associated with the root chakra and is important in invoking the Shakti energy and hence represents the door/ initiation energy for rising the Kundalini.
Because Lord Ganesh is also the key energy of this earth-plane and the ruler of the masses (Ganpati) along with "remover of obstacles" (Vignaharta), his energy is invoked before initiating any new task or journey for its smooth and successful completion
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