A streak is a challenge that is linked to (daily) tasks.
For example, capture a flag X days in a row, deploy a flag X days in a row or cap&deploy both together for X days.
A capture streak (collecting a flag daily) is relatively simple and can also be achieved by capturing Friend Flags and Eternal Flags.
A Deploy-Streak (deploying a flag daily) is much more challenging, because you must not interrupt the streak with a re-deploy or un-deploy. The Premium Membership is helpful here, because as a Premium player you can also lay out flags worldwide via the website. Deploying a Friend flag also counts for the deploy stream if it is collected by other players on the deploy day.
A capture and deploy streak are then combined together.