Well, name... you must know what sw3 does, surely? And if you don't know the basic monostable action of the 555 timer, and you are interested in electronics, then there are lots of notes on it on the web and in text books. It is an excellent place to start when learning electronics.
If you are wondering what is wrong with the circuit and why it won't work, then look at what the output of the 555 timer will be under initial conditions. Then look at what is needed to trigger the thyristor.