If you want to capture your screen and speak to make create video tutorials look no further.
Quicktime has built in functionality to record your fullscreen, part of your screen, and mic.
Event better is has share functionality build in too!
1. Select file > new screen recording
2. Select start grey triangle on the right side of the UI and select built in mic.
3. Start recording and make a selection of the screen you want to share.
See images and final video below.