A port is a location on a coast or shore containing one or more harbors where vessels can dock and transfer people or cargo to or from land. Port locations are selected to optimize access to land and navigable water while offering protection from wind and waves and facilitating commercial demand.
A marina is a dock or basin with moorings and supplies for yachts and small boats. It differs from a port in that a marina does not handle large passenger vessels or cargo from freighters.
Both ports and marinas can be displayed on the MarineTraffic Live Map with their respective icons for easier identification. All you have to do is to tick the selection boxes next to Ports and Marinas/Small Ports at the Layers section of the Live Map Toolbar.