Transistor flashing LED question

Hello,

I'm new in electronics and just started, I came across this website that have lots and lots of good circuit that beginner like me can follow. I'm looking at the following circuit and what confused me is in circuit B how does the transistor make the LED flash. Reading on transistor I can understand that it is used for switching and also for gain but can't understand how it can flash the LED ?

Thanks for the help.

hi,
The LED marked as 'flashing' is the type that has an inbuilt circuit that flashes the LED, so if you apply a DC voltage to the 'flashing' type LED it will flash at about 1 per second or so.

As the' flashing' type LED is in the Base circuit of the transistor it will also switch the transistor On/Off and the regular LED will so flash.
OK.

That make sense, thanks for your help.