Translation:I turned off the light.
Read the explanation of the use of 把 here! Basically, it's a way to change the structure of a Chinese sentence. https://resources.allsetlearning.com/chinese/grammar/Using_%22ba%22_sentences
Thank you. I don't 100% get it, but that's MUCH more clear than Duolingo's mouseover hints made it.
If you already know how to use passive voice with 被, it's essentially the same thing, but the subject and object are in the normal order. 把 simply emphasizes the relationship between the subject and object instead of the verb. I am 把 something verb.