MFi cable is an 8-pin connector which carries a digital signal. Unlike the Apple 30 pin connector it replaces (and USB Type A or B connectors), the Lightning connector can be inserted either face up or face down. Apple offers various adapters which allow the Lightning connector to be used with other interfaces, such as 30-pin, USB, HDMI, VGA, and SD cards. The Lightning to 30-pin adapter supports only a limited subset of the available 30-pin signals: USB data, USB charging, and analog audio output (via the DAC inside of the adapter).
Official Lightning USB cable contain an authentication chip that was intended to make it difficult for third-party manufacturers to produce compatible accessories without being approved by Apple; however, the chip has been cracked.
The pin out is detailed in the info box. However, each pin on the reverse side of the connector is connected to its directly opposite twin on the other side. Part of the processor's job is to route the power and data signals correctly whichever way up the connector is inserted.