Watching an episode of Daily Tech News Today i noticed there was confusion around why you would use a VPN when SSL is used prevalently. Without getting into the finer details of how VPNs and SSL works, below i will provide a simple explanation as to when you might want to use SSL and/or a VPN.
The little padlock in your browser and the web address being "https://..." indicate SSL is being used. SSL ensures the contents of any data passing to and from the website you are visiting, whilst it can be intercepted cannot be deciphered. Basically someone could see you went to amazon.com but can't see what page specifically or what your credit card details were when you bought an item.
VPN stands for Virtual Private Network. A VPN enables a user to connect to the internet through a VPN server. To hide both the content of the pages and what sites you visited from your ISP and potentially any other intruders you will want to use a VPN. Through use of a VPN, to the ISP it seems as if you are simply connected to/communicating with the VPN server.