VPNs enhance your security while enabling access to remote resources i.e. the resources to which you are not connected physically. They let you access any website, web service or an application without anyone else knowing it. No one except you knows that you visited a particular site. Not your ISP, not some hacker, not your government and not the VPN provider itself.
VPNs can help you unblock access to websites & apps such as Neftlix, Hulu, BBC iPlayer, Facebook, Twitter, etc. They also let you bypass internet censorship, access remote resources without being physically connected, download torrents and securing yourself on a public WiFi network.