What is OGG?

An open container, almost always holding Vorbis audio. Vorbis was genuinely better than MP3 and lost anyway - it's still the format of choice inside games and on Wikipedia, and still the one your car won't play.

What is Opus?

The best-sounding lossy codec at low bitrates by a comfortable margin, which is why it carries the audio in nearly every voice and video call you make. Royalty-free, equally good on speech and music, and usually wrapped in an Ogg container. It always runs at 48kHz internally.