The first step is a device lookup with "Bonjour", which allows devices to ping each other an see who's who. Any network device since the 1980s pretty much does this by default unless you disable it. Remember Netbios?
The second step, is Airdrop requesting a device to accept a connection.
At that point, you see who is sending you the send request, and you can accept/deny. Airdrop is also disabled by default from unknown senders since a dude sent a dick pick on an airplane. Your Apple device will only accept connections from known contacts by default, and you can override that setting to allow connections from anyone.
You can disable this behaviour in Settings by blocking Airdrop.
From the article: > While AirDrop’s device-to-device communications channel is typically protected from third-party snooping by its own layer of security, that wouldn’t shield someone who may have been tricked into connecting with a stranger, perhaps by tapping on a deceptively named device in a list of contacts or by thoughtlessly accepting an unsolicited connection request. This step is required for the sender to be identified, according to security experts.