It uses a kitchen timer to break work into intervals, typically 25 minutes in length, separated by short breaks.
I immediately tried it out during my recent practice sessions and am rather impressed by it’s effect. It massively helps me to focus on the task currently at hand and to ignore any distraction until the end of the pomodoro. The most interesting thing about those distractions is: I do not work on them at the end of the pomodoro. Instead, I enjoy the 5 minutes break and restart practising immediately after it. Obviously most distractions don’t require immediate action.
Admittedly, it is damn hard to practise four pomodoros (roughly two hours) in a row. At the end of the third pomodoro, my concentrativeness decreases significantly. And that’s absolutely OK. The pomodoros grant me much more focused and intense practise sessions than ever before, regardless wether i use three or four in a row.