SNAPCHAT ( is one of those online success stories that doesn’t seem to make any sense: it has millions of users, is free to use, carries no adverts, and earns no income.

And yet it’s one of the biggest new app ideas in recent years, and all the big companies want to buy it.

No wonder founder Evan Spiegel looks so happy.

So what makes Snapchat different?

It’s part photo sharing, part messaging. And crucially, it’s all disposable.

Messages are photos – often with scribbles and text captions added.

When someone sends you a Snap, the image is stored at Snapchat HQ and on your phone.

The moment you open it to take a look, a timer starts.

After a few seconds, the image is gone, deleted not just from your phone but from Snapchat’s servers too.

People love it. They love the way Snapchat messages are disposable. The only way to save one is to quickly take a screenshot before the image vanishes – so you need a sharp mind and nimble fingers.

The message sender will know that you’ve done it too, so it’s not as sneaky as you might think.

It’s not been a hit without controversy, though.

Young users love it as a way of avoiding parental monitoring, but there have been documented cases of misuse that have ended up in court.

Snapchat is a reaction to modern social networking. Facebook makes a point of saving everything, remembering your entire life for you. Snapchat saves nothing.

It’s more about sharing the moment, just for a moment. Then it’s done and gone, and time to share another moment.