FFmpeg is a utility that handles almost all multimedia formats that exist. It is usually the program that is used behind all the options of media-editing and management software. It is also used in automations like the one Google uses when we upload our videos and they convert them to all the alternative qualities.
An extensive tutorial is located here: https://img.ly/blog/ultimate-guide-to-ffmpeg/
yt-dlp is a utility that can be used as an easy method to acquire media from the internet. It supports many different websites