Totally new to this and am not sure what the difference between them are. Can anyone explain this to me in simple terms??
Since GNS3 is a replication of the Cisco IOS, the difference is as followed:
line con 0
This is the physical console port on the switch/router in which you can configure/troubleshoot the device.
line aux 0
The auxiliary port is used for out-of-band configuration of your router/switch, which is typically accomplished via a modem. The auxiliary port supports hardware flow control and the console port does not.
line vty 0 15 or 0 4
The term “vty” stands for Virtual teletype. VTY is a virtual port and used to gain Telnet or SSH access to the device. VTY is solely used for inbound connections to the device. These connections are all virtual with no hardware associated with them. This is most normal way of connecting to a router or switch and configure/troubleshoot on it.
Please remember to always use
line vty 0 15, when you configure them otherwise, you will have lines that are not protected by the configuration you use on them.