Digital Signal Processing
Electronic signals are the backbone of modern communications, but not all of them are digital. An electric record player plays sounds based on the continuous peaks & valleys of grooves in the record -- an analog signal. With each groove in each record unique, the microscopic variations in the height of the needle drive a different sound every time. If we could measure and catalogue every single molecule, every vibration, we could digitize the exact sound. But with real-world limitations, we have to squash all that variety into a range of samples. The analog gives way to the digital.