An n-p-n transistor conducts when?

When n is connected to the negative terminal or p is connected to the positive terminal of a cell/battery it is called forward biasing and when n is connected to positive terminal or p is connected to the negative terminal of a cell/battery it is called reverse biasing. In relation to the base, the emitter and collector have the following relationship:
The emitter is negative. Connected to negative terminal
The collector is positive. Connected to positive terminal.

As a result, an n-p-n transistor conducts when the collector is positive and the emitter is negative with respect o the base.