I am year one student, please explain how it work, thanks.

 

It is your classic astable multivibrator. Ignore the LEDs, they are not really needed for the circuit, though they are a great visual for the current flow. I have built a lot of those in my time.

http://en.wikipedia.org/wiki/Astable_multivibrator

 

That particular one looks like it might have trouble starting, but other than that, assume one transistor has just turned fully on and try to figure out what happens from there.

 

Thanks Bill Marsden, the wikipedia explain it all