Some ports have commodity markets and outfitters and some don't. It mostly depends on their size.
Settlements very rarely have landing pads. You can tell the difference between a port and a settlement by the icon.
Keep a Discovery Scanner handy, as ports and their planets will not show in the system map if they have not been discovered by you, even if you have a mission to visit one. In the NAV panel, unexplored planets will not show if you are able to land on them or display any ports and settlements on them until you have scanned the planet, but that info should be available in the system map if you have run the Discovery Scanner.
I think if the icon is red, then it denotes a planet that you need a landing permit for, such as Triton in the Sol system.