Describe what an oscilloscope does.

An oscilloscope is a powerful electronic instrument that primarily visualizes electrical signals by displaying voltage changes over time on a screen. This capability allows engineers and technicians to observe the waveform of signals, enabling them to analyze parameters such as amplitude, frequency, rise time, and noise. By plotting voltage on the vertical axis and time on the horizontal axis, an oscilloscope helps users to see how a signal varies over time, making it an essential tool for troubleshooting and designing electronic circuits. Understanding these voltage dynamics is crucial in diagnosing issues in circuits, ensuring proper functionality, and optimizing performance. The other options, while related to electrical measurements, do not capture the primary function of an oscilloscope, which is visual representation of voltage versus time.