Ports
What a second port is good for and how many you get.
The main port
Every instance is allocated a port when it is created. It is its own and stays with it for as long as it exists. It is in the overview and it is the port your players type.
We open every port for TCP and UDP. That is not a detail: Bedrock speaks UDP only, and so does the query function of Java servers.
Additional ports
Some plugins want a port of their own, a browser world map or a voice plugin for instance. Under Network you add one, as far as your plan allows.