What does "en0 ifscope [ethernet] " mean when run "arp -a" command in OS terminal?

Question

I run 'arp -a' and get the following message back:

apples-MacBook-Air-2:~ apple$ arp -a
hitronhub.home (192.168.0.1) at ac:20:2e:73:d4:42 on en0 ifscope [ethernet]
? (192.168.0.254) at 0:55:7b:b5:7d:f7 on en0 ifscope [ethernet]
? (192.168.0.255) at ff:ff:ff:ff:ff:ff on en0 ifscope [ethernet]

I would like to know what "en0" and "ifscope [ethernet]" fields mean?

Filtration

en0 is the interface identifer,,, in this case the first (or only) ethernet adapter that is started; ifscope identifies that the ip address (at the beginning of the line), is routed to the en0 adapter. The purpose of these fields would become more clear looking at a system with multiple interfaces (en0, en1, en2, ...) and multiple IP addresses. – Ban

i also occasionally see permanent after ifscope, to add to the question – Vampire