Kundalini is dEvi's sookshma sareeram (non physical form). It is present in the moolaadhara chakram in a coiled fashion. The coil or the concentric circle has three and half rounds.
The sakthi when induced properly by yOga, starts to flow from the moolAdhAra chakram into the swAdhishtAna chakram through a gap called Brahmmagranthi. From there to the manipoorachakram. From manipooram it flows through the vishnugranthi into the anAhata chakram and then to the vishuddhi chakram, Aagya chakram. From Agya chakram to the sahasraara chakram through the rudragranthi. Siva resides on the sahasraara chakram. Siva is immovable. So sakthi who is movable, in the form of kundalini flows from moolaadhaaram to sahasraaram and makes siva to bathe in the ocean of happiness (sudha saarabhi varshini).
This is given in the following lines of the lalita sahasranama.
moolAdhAraika nilayA brahmmagranthi vibEdini
manipoorAbja nilayA vishnugranthi vibEdini
aagyAchakrAntharAlastha rudragranthi vibEdini
sahasrArAmbujAroodA sudhA sArAbhivarshini
thatillatha samaruchi shatchakrO parisamsthitha
mahAsakthihi kundalini bisathanthu dhaneeyasi