This page explains how you can make an electrical connection within a single schematic sheet, or between one schematic sheet and another. For connection within the same schematic sheet you can use both a label and port. For connection between different schematic sheets only a port is available.
Creating Connectivity with Labels / Ports
A label is used to create connectivity to other labels with the same name, on the same schematic sheet. Only a port is available for connection between multiple sheets.
A port is available to connect a net from one schematic sheet to another, or within a single schematic sheet.
Concurrent Use of Label and Port
A label and port with different names can be placed on the same wire.