VPN stands for "virtual private network." Remember the days we used to share stuff and game over LAN (LAN stands for local area network)? The time when we could connect nearby computers through Ethernet cables and all data would go from one PC to another without any fear of being hacked. That's because that connection used to be private. That's the same thing with a VPN. In your case, it would be like establishing a connection from China to USA with the data now passing through an encrypted tunnel. With the data being encrypted, it virtually becomes impossible to poke its nose between you and the site/domain you're sending the request to/receiving data from. Maybe you can check this out for further reference and more on the subject.

https://en.wikipedia.org/wiki/Virtual_private_network

Also, about the situation in China, one of my friend is there and it's really hard to survive without a VPN. He's a student and says everybody does it, but nobody actually expresses it because Chinese authorities aren't too happy with it. He says teachers can't even get access to that vast knowledge base if they can't access sites, and it makes sense. That's why pretty much every top guy in the industry needs to keep abreast with what the world is at and it's thus, pretty much a necessity to use a vpn in china. again, check out this link for further reference. For VPNs in China, you can start your search with Googling VPNs... It does boil down to the purpose and your preference in the end but you can check out a few of them. Ivacy, Pure, PIA and Express are some names i know of.