A sensor is any component that allows a robot to collect information about its surroundings. Often, sensors are overlooked in the greater efforts to build a functioning robot, however, sensors are integral to the accurate and consistent functioning of the robot.A good overview can be found at https://docs.wpilib.org/en/stable/docs/hardware/sensors/sensor-overview-hardware.html.

Sensors might have various issues that make them be less accurate than they appear. A sensor might measure a value to many decimal points (its accuracy) but it may be measuring incorrect values for some reason (its precision). Some sensors might be affected by being too close to motors, to being plugged in on the same circuit as other devices, or by ambient light. Read documentation for your particular sensor, and be sure you know what voltage and current it expects to see on its power inputs.