Help on theory of this circuit

Hi...im a newbie in electronics and i have found a circuit on the internet.
However since im a newbie, i cant understand the working process and the theory behind this circuit. Hope those electronic experts can help on some explanation here(the longer the better)

This circuit has been discussed here in the last few months.
I cant remember which thread, but do a search using "solar".

JimB

Edit: I just did a search myself, it was you asking about it on October 17th!

yes it was me, back then i was asking whether the circuit will work or not. and now im hoping to know the explanation of the circuit, how it work etc