Apple's Native QuickTime Player allows you to record either a window or your entire screen while providing audio commentary on what you are recording. Below shows two methods that include accessing the recording feature by a key command and by accessing it through the QuickTime Player App.
Use the Screenshot toolbar
Step 1: Press Command + Shift + 5 on your keyboard. This opens your Mac’s Screenshot toolbar.
Step 2: In the center of the toolbar are two options for video recording: Record Entire Screen or Record Selected Portion. As the names suggest, you can click the left-most of the two buttons to record the whole screen or the one on the right to record just a portion.
Step 3: Click Options to tweak how it records. From here, you can screen-record on your Mac with audio. Under the Microphone heading, just choose a plugged-in mic, and when you record, your voice will be included.
Step 4: If you chose to record the whole screen, just click anywhere on your display to begin the recording. Alternatively, click the Record button.
Step 5: If you selected Record Selected Portion, you will see a box on-screen showing what will be captured. Click and drag the handles at the edges of this box to adjust what is recorded. You can move this selection to wherever you want. When you’re ready, click Record.
Step 6: When you’re finished, click the Stop button in the menu bar, or press Control + Command + Esc. A thumbnail will appear in the bottom-right corner of your desktop. Ignore it or swipe it right to save the video. Click the Thumbnail to open the recording, then click the Trim button (to the left of the Done button) to cut it if necessary. Control-Click the thumbnail to get some options, like opening it in an app or changing where recordings are saved.
Use QuickTime Player App
Step 1: Open QuickTime Player from the Applications folder, from Launchpad, or by pressing Command + Space and typing the app’s name.
Step 2: Click File > New Screen Recording or press Control + Command + N.
Step 3: This opens the same Screenshot toolbar as in the section above. Click Record Entire Screen or Record Selected Portion, then click Record.
Step 4: When you’re finished, click the Stop button in the menu bar or press Control + Command + Esc.
6. Choose File > Save, then enter a name for the recording.
You may now upload this video to YouTube if you wish to share it with many people or save it in Google Drive for future use.
Related Apple Support Articles:
https://support.apple.com/guide/quicktime-player/record-your-screen-qtp97b08e666/10.5/mac/
https://support.apple.com/guide/quicktime-player/welcome/10.5/mac