In VPOP3 a Connection tells VPOP3 how to 'connect' to the Internet.
VPOP3 supports up to 10 Connections, which can be either network connections or Dial-Up connections (using a modem)
So, when a Schedule tells VPOP3 to start a Connection, VPOP3 will start sending through the associated Mail Sender, and start collecting through the associated Mail Collectors.
In most cases nowadays, a VPOP3 installation will have a single Connection which is set to Use network for Connection. This is the case when VPOP3 connects via a router or firewall.
In some situations it may help to create multiple Connections. Some examples of when this would be useful are:
The Connection Name can contain any text. This is a name which is used in error reporting and status updates, so it can be useful to use something such as ISP name, especially if you have multiple Connections defined
In the Connector Schedule settings, you can easily tell VPOP3 to connect using the Default connections at specified times. You can designate one or more Connections as 'Default' connections, in which case they will be triggered one after the other when a Default connection is scheduled.
This allows you to easily enable/disable Connections from the Connector Schedule without having to edit the Schedule to change the specified Connections to use.