So I recently bought this item
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Unicozin Dimmable Ceiling Light with Remote Control, 8.7Inch 18W 3000K-6000K Light Color Adjustable, Round LED Flush Mount
It says N (Blue) and L (Brown).
I dont' understand, I would like to know which one is positive and which one is negative
In electrical wiring, the letter N typically stands for Neutral (Negative) and the letter L typically stands for Live (Positive). This means that the Blue wire would be connected to the Neutral wire in your electrical system, and the Brown wire would be connected to the Live wire.
However, for safety and proper installation, it is always recommended to consult the user manual or contact a licensed electrician for help with wiring your new ceiling light.