I think this is a pretty stupid question, but what are streaks? I haven't really been on Duolingo for a really long time, and I am still not sure about some parts. :p
A streak is the amount of days in a row you have practiced. Your streak is reset to 0 when you skip a day, unless of course you spend some lingots on a Streak Freeze.
Your streak how many days in a row you've practiced (and gotten some points) on Duolingo. If you miss a day, your streak will reset to zero. You get a lingot for every ten days you can keep your streak going.