Many/most microcontroller boards have analog-to-digital converters built into them, it is very convenient. E.g. it is the case for the Raspberry Pi Pico.
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An analog-to-digital converter (ADC) is an electronic device that converts analog signals—continuous signals that can vary over time—into digital signals, which are represented in discrete numerical values. This process allows analog inputs, such as sound, light, temperature, and other physical phenomena, to be processed, stored, and manipulated by digital systems, such as computers and microcontrollers.