How the Pomodoro method works
Francesco Cirillo developed the Pomodoro Technique in the late 1980s, using a tomato-shaped kitchen timer.
Pomodoro is the Italian word for tomato. The kitchen timer gave the method its name. Cirillo was a student, and he used the timer to work in short stretches instead of facing a whole evening at once.
You work for 25 minutes. Then you take about 5 minutes away from the task. After four of those work blocks, you take a longer break, often 15 to 30 minutes, and after that you can start again if you still have work. You choose one task before you start the timer.
You can use other lengths. A problem set that will not fit in 25 minutes can have 45. Reading you already know well might only need 15. Choose the length before you start, and stop when it ends, so the break is a real pause.
On this timer
Cuppafocus times a single block. It opens on 25 minutes, and you can change that before you start. The calendar day is marked when the countdown finishes. A second finished session on the same day does not add another day to the streak. The details of that mark are in How to keep a study streak going.
The next block does not start by itself. When the time ends, stand up and take the break. If you want another sitting, go back to the home page and start it yourself.
If you finish the task with time still on the clock, use what is left to check what you just did. Starting a different subject in the leftover minutes usually means the first task never gets put away.
Staying with the task
Write the task in one line you could finish, or at least move forward. "Read the next section of chapter 4" is enough. "Revise biology" is so wide that the minutes drift.
Put the phone where you cannot reach it without standing up. If a thought shows up that you are afraid to forget, write it on a scrap of paper and return to the task. Cirillo treated interruptions that way. It still works for a message you can answer after the timer.
When the time ends, leave the chair before you decide about another block. The home page will still be there.