Metadata

Wi-Fi tracking sounds super techy, but the basic idea is simple: your phone is constantly talking to the world, even when you’re not actively using it. Some people — businesses, analytics firms, even governments — can “listen in” on those signals to figure out where you’ve been and when.

In the context of mass surveillance, metadata refers to the details of your digital activities - information like who you communicated with, when, where you were, and how long the interaction lasted.