Whats the correct way to connect via FTDI to an Arduino?

Using Arduino Microcontrollers
#1

I googled several ways on how to connect via FTDI to an Arduino. For example:
FTDI ProMini

DTR -> GRN
RX   -> TX
TX   -> RX
VCC  -> VCC
CTS  -> GND
GND  -> BLK

FTDI ProMini

DTR -> GRN
RX   -> TX
TX   -> RX
VCC  -> VCC
GND -> GND

I don't understand how both can work. RX, TX and VCC are clear. But BLK, CTS, GND seem to be wired completely different - and still its working. How come?

#2

CTS is an input to the FTDI module. It can be connected to Gnd, or apparently left disconnected.
I always connect it to Gnd.
The Pin labeled BLK on the Promini is also Gnd.
The GRN and BLK refer to the Green and Black wires used in the FTDI Cable:

Schematic showing wire colors:

#3