Streak: one day counts when you do something real, not when you open the app. Days are counted in your own timezone.
Freezes: every 7 days in a row earns you a freeze, and you can bank up to 2. Miss a single day and one is spent automatically, so the streak carries on. Miss two days in a row and it starts again.
Quests: three small things each day, worth 15 XP each. They reset daily.
Leagues: earning XP puts you in this week's league with a group of other members. It closes at the end of the week and a new one starts.