Oscilloscopes handle analog, digital, serial signals

What is an oscilloscope?
Oscilloscopes are test instruments that display electronic signals (either waves or pulses) on a screen. It creates its own time base against which signals can be measured, and displayed frames can be frozen for visual inspection. It is sometimes abbreviated as CRO, for cathode-ray oscilloscope, or commonly called scope or O-scope.

What does analog mean?
A continuously varying signal. For example, if an analog signal's range is from 0V to 5V, the signal can assume any voltage within that range such as 1.2, 2.4, or 4.7V. Microprocessors and microcontrollers usually cannot process analog signals directly and require conversion by an A/D converter before they can process the signal.