This is a TTL shift registers they use voltage source when using the 3V-5V. And it is often used along with the support of the NE555 oscillator in the lab. Image simulation.
How it works: we only need to change in logic value at pin 1 of the 74LS164 is running you will see a change in the value of the led out.
P / S: Do we only have one class hour his practice should only do this to support you. Wish you have a practice test session to achieve good results.