In Kabbalah a Zivug (spiritual intercourse) is a coupling that occurs between the Ohr (Light) and the Kli (vessel). In other words, it is a union of the masculine with the feminine.
There are two types of Zivugim - Zivug de Neshikin (kissing) and Zivug de Yesodot (named for Yesod. Zivug de Neshikin occurs when the interior of the masculine emanation unites with a feminine. Zivug de Yesodot is when exterior of the masculine emanation unites with a feminine. The latter Zivug happens after the former, and from this Zivug are emanations spread to the worlds.
After TA (Tzimtzum Aleph) in the world of AK (Adam Kadmon), all the spiritual objects were given a Masach on vessel Malchut so the Upper Light would not be received inside Behina Dalet (also known as the creature or reception for the sake of reception).
The instant the Upper Light attempts to enter the Kli through the Peh, the Kli asserts its TA and uses the Masach to push away the Ohr Yashar (Direct Light). This, the process of Zivug de Haka'a, causes the lifting of the Ohr Hassadim (Reflected Light) which dresses itself onto the ten sefirot of the Upper Light and forms the first ten sefirot at the Rosh of the Partzuf.