What is Sound in the Computer?
Sound are vibrations in the air that we perceive with our ears. These vibrations are also called sound waves. Just like waves on the sea, a sound waves have their ups and downs. We can think of how intense the vibrations are as a wavy line. We can measure the intensity of the waves, the height of the wavy lines, with a sound recorder, and store this data in some medium, such as a vinyl disc. Then we can reproduce the sound by making something vibrate in such way that it creates sound waves of exactly the same intensity as we recorded.
Digital sound is based on the same principle as vinyl discs. The sound isn't recorded as grooves on vinyl, but as numbers instead. In the lossless 16-bit PCM audio codec, one second of audio at 44100hz literally means we have 44100 numbers in sequence in a .wav file that tells us the shape of the sound wave. In other words, we measured the sound wave intensity 44100 times per second, and just saved the number, so we can reproduce it later. As always, the data captured in real life is analog data, while the data in the computer is digital data (it's bits, 1's and 0's). In order to reproduce audio, your CPU sends the audio bits to a sound card, which means the sound card has a bunch of electrical circuits in parallel through which electricity runs when a bit is 1. More specifically, when a bit is 0, there is no voltage in a circuit, and when a bit is 1, there will be some voltage. The job of the sound card is to take this information and turn it into an analog signal, which means it will take this fixed amount of voltage and turn it into varying amounts of voltage. This analog signal is then sent to the sound speakers, which convert electricity into magnetism to make things vibrate, and that's how sound works.