Ports are like connectors between nodes, each node has at least one Port, to connect a Port to another, click and hold on the desired Port, drag your mouse to the Port you want to connect to, and release mouse.
There are two types of Ports, IN which is always on the left, and OUT which is always on the right, these two types can only be connected to each other, no Ports of the same type can be connected.
Ports have different data types, each Port can be only connected to another Port with the same data type, unless the Port data type is convertable, or the Port can change its type.
Port data types can be identified by two attributes:
Color: Each Port data type has a different color.
Name: Each Port data type has its type written in capital letters next to it.

Ports have two states:
Normal: when the port is not connected, only the outline of the Port colored.
Connected: when the port is connected, which the whole Port is colored.