Its basically the convergence 'Zone' of air masses and as such usually affects the weather pattern along the tropics.
It keeps the 'date' with the movement[apparent] of the Sun, going high [higher latitudes] during the Summers in the N hemisphere and lying much South during the winters [summer for S hemisphere].
Even the 'Great Migration' in Africa bordering Tanzania/Kenya is played out as per the ITCZ movement. ITCZ also extends across the Indian sub-continent though not displayed on Sig Wx charts.
Check the British Museum at London for an great animated display.
