If you need a tool to record commands in your terminal, including their input and output, take a look at https://github.com/asciinema/asciinema.
It records your terminal session and allows you to upload them to their archive, which then you can share with the world, or download the media file.
If you want to generate GIFs without uploading your sessions, there’s also: https://github.com/asciinema/asciicast2gif
If that still doesn’t meed your requirements, try https://github.com/phw/peek. Similar to GNOME’s screen recorder, but with more flexibility.
Finally, if you need to record a voice over, I would recommend you the go-to tool for streaming and recording video: OBS
This is a micro-post about the GNU/Linux environment, its main purpose is to highlight and redirect to valuable resources.