I’ve always said it’s like the modern CB radio. CB radios were (and still are) used for short bursts of speech – an open broadcast. Twitter is exactly that but it’s online instead of the radio waves.
Where you’d hold the button and speak into the radio mic, you now type and press tweet.
The radio waves went in every direction, arriving to everyone with an aerial. The same for Twitter when you tweet – the world can see it if they’re online and tune into your message.
On a CB radio, you can preface your broadcast with someone’s name to call them out directly, not just address the world. Exactly the same on Twitter, so we all get a handle (Twitter call it a user name) that can burst a message to the world or we can talk directly to people by using their handle.
Congratulations, we are all the modern version of Burt Reynolds in Smokey And The Bandit!