Concerns regarding Swagbucks app

I received a notification that Swagbucks was draining my battery. I thought that was weird because I closed all applications on my phone. I guess the app was still running in the background or in some way in which closing apps on your phone does not close the Swagbucks app. This also makes sense considering I cannot swipe away some of the notifications I get from Swagbucks. I just have to wait and the next time I look at my phone they are gone. It's like the app is running with extra permissions or something. Anyone have some insight?