A VPN is a virtual private network. A network is when two or more computers are connected and can share information. A private network is when the connected computers are isolated from other computers and the Internet and can only share information with each other.
A virtual private network is a way to create a private network without being completely isolated from other computers.
A VPN creates a private network by creating a secure tunnel to a server designed to be shared and one that deletes its logs. You connect securely and encrypted to the server and it relays your request to the website of your choosing. The website you go to, only knows that the server you are connected to has requested to connect. You are just one of many people connecting to this server and if someone like the FBI tries to find out who went to a specific website, they will find out the information is not available.
If you ISP wants to slow down movie streaming for everyone, you will not be affected as they do not know what information you are transferring. If they were able to copy packets in an effort to find out what you are doing, they will find them encrypted and so hard and expensive to decode that it is not worth the time or expense.
A VPN is a must have if you pirate movies, games or software. but that is not the only reason to use a VPN. By freely giving Google and your ISP and many other interested parties your information, you become a commodity to be used and manipulated by them so they make money. Just like the family whose life changed in a instant by the FBI crashing into their home your life could be interrupted too. He had been looking at buying some black power for his primitive rifle while earlier she was looking for a new pressure cooker for canning vegetables. Those two things added up to terrorism.
A large aspect of your life is now being scrutinized by others over the Internet. All of the things you do and the data they are tracking and saving is NONE OF THEIR BUSINESS!