Basics - VIDYARAMBH
Dharmic literacy 101
YANTRA : It is one of the fundamentally universal concept that is present in almost all the branches Kulas ,schools of Hinduism except Bhakti marg.
Yantra - YAN - to travel or transcend
TRA - a medium .
So Yantra is a medium to travel or transcend to another level. When Yantra is connected to any Devi or Devata then , it is a way to travel or connect to the universe of that devi or devata.
It is the physical representation of the universe of Devata. It has many yogini, Devatas, Bhairavas that guard the entry of the universe until you reach the center of the Yantra where the Devi/Devata resides.
Not all Yantra contains geometry. To invoke the deity into the Yantra is like tuning the radio to catch the right frequency.
All my knowledge comes from my Guru Kaulantak Nath Ishaputra.
Om sam siddhaya Namaha
Om Gan Ganapataye Namaha