Watch your host ask for a MAC address. L3
Your host knows the next hop's IP. But Ethernet needs a MAC. ARP is how it asks the entire LAN, and one device answers.
Local Network · 192.168.1.0/24
You
192.168.1.10
aa:bb:cc:00:00:10
Gateway
192.168.1.1
aa:bb:cc:00:00:01
Laptop
192.168.1.42
3c:22:fb:01:02:03
Server
192.168.1.100
de:ad:be:ef:00:01
Printer
192.168.1.55
00:11:22:33:44:55
Who has this IP?
ARP Cache (ip neigh show)
ARP cache is empty. Resolve an address to populate it.
Type an IP on this subnet. Your host will broadcast an ARP request to the entire LAN: "Who has this IP? Tell me your MAC." If a device owns that IP, it replies with its MAC address. If nobody answers, the frame can't be built.
host:~$