Classic 25/5 is a preset with 25 min of focus, a 5 min short break, and a 15 min long break. You take a long break after every 4 focus sessions.
This is the standard Pomodoro proposed by Francesco Cirillo. You focus for 25 minutes, break for 5, and after every four focus sessions take a 15‑minute long break. It's a balanced rhythm that works well for most people, which makes it the top recommendation when you're just starting out.
25 minutes is short enough to start a task you've been putting off without feeling overwhelmed, yet long enough to really immerse yourself in one task. If you're not sure which rhythm suits you, start here.