Your streak is the number of consecutive days you've learned on Brilliant. Your current streak count can be found on your home page.
To extend your streak, you must complete either 3 problems or a full lesson in a single day. Each qualifying day of activity increases your streak count by one.
If you miss a day, your streak resets to 0—however, if you have an available streak charge, you will instead lose a charge and your streak will stay the same.