A HDMI cable typically has 19 pins, although there are also mini and micro HDMI cables with fewer pins. HDMI 1.3 and earlier had 8 pins in three rows, while HDMI 1.4 added a fourth row of 5 additional pins to support the new features of that version – Ethernet over HDMI and Audio Return Channel.
To answer your question more directly, there are different types of wires within the actual physical structure of the cable itself – there are 4 twisted pairs for each differential data channel (for a total of 8 data channels), plus 3 additional ground wires solely for providing proper termination and impedance control for canceling crosstalk.