What' s the difference between a forward proxy server and a reverse proxy?

I'm so confused, I know a proxy acts as a barrier towards the Internet and I also know it can get into private servers. But why would you need either a forward or reverse one, and what does each one do?
Thanks xxx

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…).