What are the different internet connection types used by ifconfig and ipconfig?

These are properly known as BSD names, so you can look at the BSD / Darwin source code to see what these mean.

• en is Ethernet
• lo is loop back or local host
• awdl is air drop peer to peer (a type of mesh network)
• bridge is a connection between networks
• p2p is sometimes a virtualization link and also some people have reported it being used with AirDrop before that changed to be awdl0

The numbers added to the end just increment as you add a second interface of the same type. The rest are tunneling interfaces for VPN and bridging between IPv4 and IPv6:

• see Ian's answer on question Unexpected interfaces in ifconfig