There are times when people need to use a computer - and not leave a trace.
Now, a clever piece of software lets one carry their own personal computer, which can easily be carried inside the pocket - and once the person has finished using it, no one will ever know.
Technically, the PC that people would be carrying is not a whole computer - instead it is a simple USB memory stick. Bit within it is a full operating system like Windows, and when you plug it into a PC, that computer will restart into your own personal setup, called Tails.
When you have finished simply shut down the computer, put the USB stick back in the pocket, and the PC will never know that it has been used. As everything the user odes is contained within Tails, the software on a stick, not a single trace is left on the original PC. That means no cookies of the website browsed, no chance of documents being left in a recycle bin.