As there have so far been no questions on the first term- tzaddik, I’ll move on to the next one- the Zohar says, “Ispashtusa dMoshe bchol Dara vdara,” there is an extension of Moshe Rabbeinu in every generation.
Chassidus explains this in many places to mean that every generation has a tzaddik (see above) who is the Moshe Rabbeinu for that generation. Just like the original Moshe Rabbeinu, all the needs, physical and spiritual, come through this tzaddik.
There is another intertwined concept that all the neshamos are like a body. The neshamos not affected at all on their journey down to the world are the head and brain of klal Yisrael- our tzaddikim and leaders. The lowest neshamos, or the ones most affected by their journey, become the least spiritually in tune Jews- they have a hard time connecting to their neshama and connecting to Hashem. They are compared to the feet. Following this ever neshama has it’s place in the “body” of knesses yisrael, and just like the brain directs the body our leaders for. Just as the brain is the same essence as the father’s brain- the head neshamos are the ones most similar to Hashem’s Chochma.
And it is through these neshamos that everyone else gets their spiritual life force.
This and more is explained in perek beis of Tanya, the tzaddik concept is in perek aleph.
So far nothing controversial, this is like chassidus 101 and well known to I would think all lubavitchers. Any questions?