Can someone please explain this simple NPN circuit?

Yep :stuck_out_tongue:

Anther thing that confuses me, the real circuit flows from negative to positive?

My negative battery lead is ground in my real circuit and it works, but if i switch positive for negative, it doesnt work.

In other words, only conventional flow works with this circuit.

I'm so confused :stuck_out_tongue:

Wish i could take a pic of my breadboard so someone could see it, but i will try explain it.

The transistor has its flat square edge facing me.

My positive battery lead, the red one, is first, connected to one side of an led, the other side of the led is connected to one side of a 330 ohm resistor, the other side of the resistor is plugged into the right pin of the transistor. (collector)

The middle pin is connected to arduino digital out pin 13 via a 10k resistor. (base)

The negative lead of my battery and arduino ground pin ar connected to the left pin of transistor. (emitter)

This circuit works but i dont understand why.

It makes sence if electrons flow from red lead to black. But if they flow from black to red, i dont get it.