Ask for the principle of LM2596S-5.0 Voltage Regulator's step -down

Hi, thank you for ur reading first!

I want to design a DC/DC circuit, which is to reduce 12V to 5V. I searched for it on wiki and others, even saw an article introduce it in detail. But I can not find the relatives about the principle of its step-down. So I am still confused.

Can you tell me about the principle of the LM2596S-5.0 Voltage Regulator's step-down?

Thanks in advance!