The AN port is also known as O-ring boss. This is the side of the adapter that screws into the fuel rail, fuel pressure regulator, fuel filter, fuel pump etc. The AN flare side is what connects to the female hose end.
Note: On the drop down menu when selecting the size you the first number is the flared side and the 2nd number is the O-ring boss side (ORB).
Example: AN 8 to AN 8 ORB