Analog data is data that is represented in a physical way. Where digital data is a set of individual symbols, analog data is stored in physical media, whether that's the surface grooves on a vinyl record, the magnetic tape of a VCR cassette, or other non-digital media.
One of the big ideas behind today's quickly developing tech world is that much of the world's natural phenomena can be translated into digital text, image, video, sound, etc. For example, physical movements of objects can be modeled in a spatial simulation, and real-time audio and video can be captured using a range of systems and devices.
Analog data may also be known as organic data or real-world data.