What is MOV?

QuickTime, and what a Mac or an iPhone records into. Structurally it's almost the same file as an MP4 - both grew from the same specification - but plenty of software sees the extension and refuses anyway, which is the entire reason MOV to MP4 is a conversion people need.

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.