You may have heard that London cabbies are planning to gridlock London streets today as part of a demo against a smartphone app.

The black cabbies are set to demonstrate against the Uber app on 11 June.

Why are cabbies demoing against Uber?

According to the law, only black cabs licenced by TfL are allowed to use fare meters in London.

Uber equips its drivers with a smartphone app that works out fares by being connected to a remote server. The app takes into the account the time taken and the distance travelled, just like a black cab meter.

The union that represents the black cab drivers (the Licensed Taxi Drivers Association) believes that the app is acting as a taximeter and is therefore illegal.

Transport for London (TfL) believes that since the Uber smarphone app is not physically connected to the vehicle, like the meters in black cabs, the app is legal.

TfL has asked the High Court to investigate whether the Uber app is breaking the law but this has not stopped the protest going ahead. Uber said it welcomed TfL's move to try and settle the matter at the High Court.

What is Uber

Uber is a San Francisco-based company, founded in 2009. It describes itself as a "pick-up" service that connects passengers with vetted private drivers.

Uber's app (backed by Google and integrated into Google Maps) allows customers to order taxis through their smartphone, see who their driver will be, and track the arrival of their car.

Uber operates in over 100 cities across 30 countries. It launched in London in 2012 and in Manchester in May.

Where can I get an Uber cab?

The Uber car service already operates in London, Manchester and in other countries.

How does Uber work

You need to download the Uber app to your smartphone and sign up. To create your account you will need to enter your credit card number. It doesn't take long to register.

To download Uber for your iPhone click this link.

When you wish to use the service you do everything from the app - you'll never need to call a cab firm again. Your location will be pinpointed using the GPS in your phone (although you can define it if necessary).

You can choose the type of vehicle you need.

Once you have made your selection you will be told how long the wait for your cab will be.

At the end of the journey you don't need to pay anything as the company already has your credit card details. You will get an email the following day including a breakdown of costs.

Are Uber cabs safe

The Uber cab drivers are vetted, so they should be safe. But exercise the same caution you would getting into any cab.

When you end a journey you are able to rate a driver,

How much does an Uber cab cost?

The fare depends on a number of factors. The car you choose, the traffic, even the weather. And obviously the distance.

How does Uber make money?

Uber makes its money by taking around 20 percent of its drivers' fares.

Uber agro elsewhere

Uber has also faced opposition in Milan, Paris, Spain, has already been banned in Brussles and is in a court battle in Berlin.