Audio encoding is just simply translating audio signals to digital. By nature, audio is analog signal. Your voice is analog, any sound you hear is analog. Now for this signal to be able to transmitted over the internet or any digital medium, it should of course be converted to digital signal. Analog signals are in the form of waveforms, whereas digital signals are in binary form, with bits of 0s and 1s. To be able to be interpreted by the computer, an analog signal should be converted to a digital signal. Various formats of digital audio are MP3, WAV, OGG, etc. Now what the audio encoder does is it simply converts your analog audio signal to digital audio signal. On the technical side, audio encoding involves sampling of the analog signal per given time (around a few milliseconds ideally), holding the sampled value, comparing it to a certain threshold voltage. The sampled voltages are then converted to binary values. To make it simple, just imagine you have a handwritten text on a paper. Then you encode it on a computer, then you become the encoder. In the case of audio, a device, listens to the audio, and converts it to a format readable by your computer. Audio encoding is the process of converting your audio signal into a format readable by your computer, which is then can be transmitted through a digital transmission medium.