Question: I just recorded a video conversation using the 'screenshot' function on my mac. The idea was to record the video call, but also the audio of me and the other person talking... There was NO audio recorded!

How to record audio from the screen?!

Answer: 
I came across the same problem when we went to online teaching after SARS-CoV-2 hit. I found a free workaround, but there are subscription services that work. I can't say for sure that this is the best way to do it (just best for right now?):

1. Open a web-conferencing app like Zoom, WebEx, GoToMeeting, etc., and start a meeting without others.
2. Share your screen in the meeting, focussing on the video you want to record. Make sure you select to "Share computer audio" in this step.
3. Now open your preferred screen-recorder such as Screencast-O-Matic, Canvas Studio, Echo360, etc. (I don't know if the built-in recorder works), and record the shared web-conference video.

I hope this was helpful, but I look forward to better options if anyone has any! Good luck!
It is possible to capture system audio during a screen recording if you install an audio driver extension such as [BlackHole](https://github.com/ExistentialAudio/BlackHole) or [iShowU Audio Capture](https://obsproject.com/forum/resources/os-x-capture-audio-with-ishowu-audio-capture.505/). Both are free. When installed they become an additional sound input which may be selected like the internal microphone.