What are you doing? Seriously. Right now I’m typing. I had a shower earlier. Later I may go to the cinema or watch TV. I need to do laundry. I ate Thai food at Cafe Asean in Manhattan last night. Green shrimp curry. I like it there. Do you care? Apparently so.

Just three years old, San Francisco-based Twitter has become the hottest internet firm on the planet, simply by asking people that question. Industry analysts reckon 15m people a month are now sharing what they are doing via Twitter.

And its founders, Jack Dorsey, Biz Stone and Evan Williams, believe they have created the next wave of communication, something beyond e-mail, texting and social networking.

When I saw them recently in their San Francisco offices, Stone described Twitter as a new form of human communication, “like a flock of birds choreographed in flight”. It’s a huge claim, but then look at other technologies that have changed the world, from the fax to YouTube. Individually, a single fax or some video of a child high on dental drugs tells you nothing.

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BACKGROUND

• Even the Travel Tweeters are staying in the UK this summer

• The Truman show has arrived. It’s called Twitter

• Bucharest/Budapest - the difference? £826

• Roman Catholics told to Twitter prayers

Yet the simple fax sped up the world, making it impossible to pretend that the letter was in the post. YouTube was a big player in the US elections, and sparked a political furore in China with a video allegedly showing Tibetan monks being beaten by Chinese soldiers.

By bringing crowds of people together in real time, Twitter’s founders believe they, too, could herald a profound change in the way the world communicates. The flock is spreading by the hour, up 1,000% on last year. But do they have the remotest idea where the flock is heading?

Everyone from Barack Obama and Britney Spears to Jonathan Ross and Eddie Izzard is Twittering. So are a number of MPs, Boris Johnson and 10 Downing Street — all Twits. During the Mumbai terrorist attacks in December, people Twittered from their hotel rooms. Barack Obama’s inauguration was one big Twitathon.

In Britain the number of people using Twitter has risen 32-fold in the past year — it now has more visitors than the travel site Expedia.co.uk. All the Twits in London, the Twittiest city in the world apparently, managed to crash parts of the website during the recent G20 meeting.

If you’re living in a cave (I’m talking to you, Bin Laden) and have no idea what all of this means, here’s a simple explanation: Twitter is a cross between e-mail, text messaging, blogging and Facebook. It sounds complicated, but the secret of Twitter’s success is that it’s very simple, says Stone. “There isn’t a big learning curve here. You can just sign up and get on with it.”

Twitter allows you to post messages from your computer or a web-enabled phone to the web. No managing your Facebook page or thinking up lengthy, well-reasoned blog postings. Messages, known as tweets, are limited to 140 characters.

They can link to websites, videos or pictures, or Twitpics. You can “follow” other users and they can “follow” you, meaning you get all their messages as they post them and vice versa. Twitter is a place where you receive messages only from people you want to hear from and you need never reply. It’s e-mail without responsibility.

Unless you choose otherwise — and few do — anyone can see what you are up to. If you really want to know what I’m having for breakfast, just look me up. If it all sounds unbelievably banal, you’re right — and you’re also very, very wrong.

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