internet trackers collect information on your browsing activities. often this is employed for marketing, but data can also be exploited in more harmful ways.
VPN (virtual private network) creates a secure connection to another network over the internet. this eliminates 3rd party snooping and also gives the same network functionality as being at that location (such as, accessing campus-restricted library resources!). there are applications that can help set up a VPN, or it's possible to build your own.