Can someone explain to me how Google Ad sense works and if there are any hidden costs or rules?

Also can someone explain to me how to use google ad sense and if there are any hidden rules and costs which do not allow me to use it. Is it safe and will it require a popular website.

What is a VPN?

VPN is (Virtual Private Network) were first used by companies to enable their employees to securely access internal systems such as email remotely (e.g. from home or while on business trips). Today they are increasingly being used for personal use by individuals to protect their privacy while online in public places (e.g. when using the wi-fi connection in a cafe) or in a country where the internet is censored / blocked (e.g. China, Saudi Arabia…).