Yichud means unification and comes from the root word יחד unified or one. A Yichud is a type of a kavana - special Kabbalistic intention.
Man's role consists in the restoration of the original harmony that was destroyed with the breaking of the Vessels; the unification of the name of G-d.
The Arizal says that our role is to restore the connection between the two facets of G-d the Yud+Hey/ Vav +Hey, the intellectual and emotional parts of G-d’s names thereby uniting the above nature and nature realms.
This reuniting process are known as Yechidim, "Unifications". A great many yechidim were taught. All involve the meditative contemplation of the letters of the various names of G-d.
Israel, Torah and G‑d are bound together in complete unity, as the Zohar states...
Access Live Kabbalah's complimentary in-depth Class & PDF Notes on Reincarnations- The secret of the Gilgul, Kabbalah & Judaism's approach on reincarnations.