How does the China Public Health Care System work?

I have been told that working in China, I must join the China Public health care system. I have read the one page that explains briefly about the system and opinions, but it is not clear. My company is willing to pay 80% of the fee which sounds okay. I will need to pay 200RMB per month for insurance. Is it really mandatory in Guangzhou for all staff to join? Is that normal? Are there better possible options for Foreign English teachers teaching in China? Secondly, I have searched and asked for more information on what exactly the Chinese Public health system covers but the information I have received is not really making it clear on what I am covered for? For example does it cover dental, checkups, simple things if I get sick and need to see a doctor, pregnancy, or more serious health issues? Is there a percentage that I need to pay when I visit the doctor? If someone has a detailed list or explanation on the China Public Healthcare system, it would be really appreciated for me and other teachers.